The Collider Detector at Fermilab may have found some unexpected particles (Fermilab)
[/caption]If you thought any quantum discoveries would have to wait until the Large Hadron Collider (LHC) is switched back on in 2009, you’d be wrong. Just because the LHC represents the next stage in particle accelerator evolution does not mean the world’s established and long-running accelerator facilities have already closed shop and left town. It would appear that the Tevatron particle accelerator at Fermilab in Batavia, Illinois, has discovered…
…something.
Scientists at the Tevatron are reluctant to hail new results from the Collider Detector at Fermilab (CDF) as a “new discovery” as they simply do not know what their results suggest. During collisions between protons and anti-protons, the CDF was monitoring the decay of bottom quarks and bottom anti-quarks into muons. However, CDF scientists uncovered something strange. Too many muons were being generated by the collisions, and muons were popping into existence outside the beam pipe…
The Tevatron was opened in 1983 and is currently the most powerful particle accelerator in the world. It is the only collider that can accelerate protons and anti-protons to 1 TeV energies, but it will be surpassed by the LHC when it finally goes into operation sometime early next year. Once the LHC goes online, the sub-atomic flame will be passed to the European accelerator and the Tevatron will be prepared for decommissioning some time in 2010. But before this powerful facility closes down, it will continue probing matter for a little while yet.
In recent proton collision experiments, scientists using the CDF started seeing something they couldn’t explain with our current understanding of modern physics.
The particle collisions occur inside the 1.5 cm-wide “beam pipe” that collimate the relativistic particle beams and focus them to a point for the collision to occur. After the collision, the resulting spray of particles are detected by the surrounding layers of electronics. However the CDF team detected too many muons being generated after the collision. Plus, muons were being generated inexplicably outside the beam pipe with no tracks detected in the innermost layers of CDF detectors.
CDF spokesperson Jacobo Konigsberg, is keen to emphasise that more investigations need to be done before an explanation can be arrived at. “We haven’t ruled out a mundane explanation for this, and I want to make that very clear,” he said.
However, theorists aren’t so reserved and are very excited about what this could mean to the Standard Model of sub-atomic particles. If the detection of these excess muons does prove to be correct, the “unknown” particle has a lifetime of 20 picoseconds and has the ability to travel 1 cm, through the side of the beam pipe, and then decay into muons.
Dan Hooper, another Fermilab scientist, points out that if this really is a previously unknown particle, it would be a huge discovery. “A centimetre is a long way for most kinds of particles to make it before decaying,” says . “It’s too early to say much about this. That being said, if it turns out that a new ‘long-lived’ particle exists, it would be a very big deal.”
Neal Weiner of New York University agrees with Hooper. “If this is right, it is just incredibly exciting,” he says. “It would be an indication of physics perhaps even more interesting than we have been guessing beforehand.”
Particle accelerators have a long history of producing unexpected results, perhaps this could be an indicator of a particle that has previously been overlooked, or more interestingly, not predicted. Naturally, scientists are quick to postulate that dark matter might be behind all this.
Weiner, with colleague Nima Arkani-Hamed, have formulated a model that predicts the existence of dark matter particles in the Universe. In their theory, dark matter particles interact among themselves via force-carrying particles of a mass of approximately 1 GeV. The CDF muons generated outside the beam pipe have been calculated to be produced by an “unknown” decaying parent particle with a mass of approximately 1 GeV.
The comparison is striking, but Weiner is quick to point out that more work is needed before the CDF results can be linked with dark matter. “We are trying to figure that out,” he said. “But I would be excited by the CDF data regardless.”
Perhaps we don’t have to wait for the LHC, some new physics may be uncovered before the brand new CERN accelerator is even repaired…
Artist's impression of gravitational waves. Image credit: NASA
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Everyone loves a theme. And this week we’ve collected together some of your questions about relativity. More light speed spacecraft, twin paradoxes, and the mixing up of gravity, time and mass. If you’ve got a question for the Astronomy Cast team, please email it in to [email protected] and we’ll try to tackle it for a future show. Please include your location and a way to pronounce your name.
As if gamma-ray bursts (GRBs) weren’t mysterious enough, there’s something else to add to the bag of confusion. GRB events are missing from the furthermost reaches of the Universe. Right around the time when there should be a lot of GRBs, during the “star forming epoch” (when stars were just beginning to evolve after the Big Bang), there appears to be none. Zero. There’s no ancient flashes of massive star death to be found. What’s more, there doesn’t appear to be any afterglow from previous gamma-ray bursts either.
So what’s going on? Were there no GRB events before 12.8 billion years ago? Possibly… although there might be another answer. They are out there but we just can’t see them.
Gamma-ray bursts are the biggest and brightest explosions in our Universe since the Big Bang. When a GRB detonates, it can easily outshine its host galaxy containing billions of stars. These energetic events have been observed since the 1960’s and only until recently have astronomers found an explanation as to what GRBs are. A GRB occurs when a young metal-poor massive star has used up all its fuel and, like a supernova, collapses under its own gravitational field. The rapid-spinning star then funnels intense beams of radiation from its poles in the form of gamma-rays. Should one of these beams be directed toward Earth, we see a disproportionately bright explosion (as a vast amount of energy is channelled through the poles). Until the “collapsar model” was devised, astronomers were at a loss to explain these energetic events.
The collapsar model appears to explain GRBs lasting for two seconds or more. However, there is another class of GRB, of much shorter timescales, that does not fit in with the collapsar model. Short-period GRBs may be the result of violent interactions between black holes and a neutron stars.
So, does this mean GRBs are becoming less mysterious? Actually, GRB theory has just become a little more complicated. It would appear that no GRBs occurred before 12.8 billion years ago. Last month, the most distant (and therefore oldest) GRB was detected 12.8 billion light years away, but that in itself is strange.
During the time when the first stars started to form (around 13.4 billion years ago), they were by definition “metal-poor” stars (heavier elements, such as metals, were only possible after several generations of stellar evolution), so this should be a period of time when GRBs were regularly lighting up the night sky. However, according to observations of the most distant galaxies containing the youngest stars, GRB events seem to be non-existent.
One explanation put forward is the effect of red shift. As the Universe expands, space-time stretches. As light travels from the most distant reaches of the Universe, perhaps the light itself from GRBs has been so stretched (red-shifted) that the electromagnetic emissions simply cannot be detected by our instrumentation. These huge explosions could be happening, but as the emitted light has been so red-shifted, by the time the light reaches us, perhaps the emission does not resemble a GRB. Even the afterglow of one of these massive explosions would be unrecognisable in this case, the light observed would be shifted all the way into the infrared.
So will any GRBs be discovered further away than 12.8 billion light years? I think we’ll have to wait until we build some improved infrared observatories or recognise what a distant, ancient GRB looks like…
Could the magnetic field of the Earth really reverse in 2012? I wouldn't bet on it...
[/caption]Apparently, on December 21st 2012, our planet will experience a powerful event. This time we’re not talking about Planet X, Nibiru or a “killer” solar flare, this event will originate deep within the core of our planet, forcing a catastrophic change in our protective magnetic field. Not only will we notice a rapid reduction in magnetic field strength, we’ll also see the magnetic poles rapidly reverse polarity (i.e. the north magnetic pole will be located over the South Pole and vice versa). So what does this mean to us? If we are to believe the doomsayers, we’ll be exposed to the vast quantities of radiation blasting from the Sun; with a reversing magnetic field comes a weakening in the Earth’s ability to deflect cosmic rays. Our armada of communication and military satellites will drop from orbit, adding to the chaos on the ground. There will be social unrest, warfare, famine and economic collapse. Without GPS, our airliners will also plough into the ground…
Using the Mayan Prophecy as an excuse to create new and explosive ways in which our planet may be destroyed, 20 12 2012 doomsayers use the geomagnetic shift theory as if it is set in stone. Simply because scientists have said that it might happen within the next millennium appears to be proof enough that it will happen in four years time. Alas, although this theory has some scientific backing, there is no way that anyone can predict when geomagnetic reversal might happen to the nearest day or to the nearest million years…
Firstly, let’s differentiate between geomagnetic reversal and polar shift. Geomagnetic reversal is the change in the magnetic field of the Earth, where the magnetic north pole shifts to the South Polar Region and the south magnetic pole shifts to the North Polar Region. Once this process is complete, our compasses would point toward Antarctica, rather than northern Canada. Polar shift is considered to be a less likely event that occurs a few times in the evolutionary timescale of the Solar System. There are a couple of examples of planets that have suffered a catastrophic polar shift, including Venus (which rotates in an opposite direction to all the other planets, therefore it was flipped upside down by some huge event, such as a planetary collision) and Uranus (which rotates on its side, having been knocked off-axis by an impact, or some gravitational effect caused by Jupiter and Saturn). Many authors (including the doomsayers themselves) often cite both geomagnetic reversal and polar shift as being one of the same thing. This isn’t the case.
So, on with geomagnetic reversal…
How often does it happen? The Earths interior (University of Chicago)The reasons behind the reversal of the magnetic poles is poorly understood, but it is all down to the internal dynamics of Planet Earth. As our planet spins, the molten iron in the core flows freely, forcing free electrons to flow with it. This convective motion of charged particles sets up a magnetic field which bases its poles in the North and South Polar Regions (a dipole). This is known as the dynamo effect. The resulting magnetic field approximates a bar magnet, allowing the field to envelop our planet.
This magnetic field passes through the core to the crust and pushes into space as the Earth’s magnetosphere, a protective bubble constantly being buffeted by the solar wind. As the solar wind particles are usually charged, the Earth’s powerful magnetosphere deflects the particles, only allowing them into the polar cusp regions where the polar magnetic fieldlines become “open.” The regions at which these energetic particles are allowed to enter glow as aurorae.
Usually this situation can last for aeons (a stable magnetic field threaded through the North and South Polar Regions), but occasionally, the magnetic field is known to reverse and alter in strength. Why is this?
A chart showing Earths polarity reversals over the last 160 million years. Black = normal polarity, White = reversed polarity. From Lowrie (1997)
Again, we simply do not know. We do know that this magnetic pole flip-flop has occurred many times in the last few million years, the last occurred 780,000 years ago according to ferromagnetic sediment. A few scaremongering articles have said geomagnetic reversal occurs with “clockwork regularity” – this is simply not true. As can be seen from the diagram (left), magnetic reversal has occurred fairly chaotically in the last 160 million years. Long-term data suggests that the longest stable period between magnetic “flips” is nearly 40 million years (during the Cretaceous period over 65 million years BC) and the shortest is a few hundred years.
Some 2012 theories suggest that the Earth’s geomagnetic reversal is connected to the natural 11-year solar cycle. Again, there is absolutely no scientific evidence to support this claim. No data has ever been produced suggesting a Sun-Earth magnetic polarity change connection.
So, already this doomsday theory falters in that geomagnetic reversal does not occur with “clockwork regularity,” and it has no connection with solar dynamics. We are not due a magnetic flip as we cannot predict when the next one is going to occur, magnetic reversals occur at seemingly random points in history.
What causes geomagnetic reversal? The model Earth, can a magnetic field be modelled in the lab? (Flora Lichtman, NPR)Research is afoot to try to understand the internal dynamics of our planet. As the Earth spins, the molten iron inside churns and flows in a fairly stable manner for millennia. For some reason during geomagnetic reversal, some instability causes an interruption to the steady generation of a global magnetic field, causing it to flip-flop between the poles.
In a previous Universe Today article, we discussed the efforts of geophysicist Dan Lathrop’s attempts to create his own “model Earth,” setting a 26 tonne ball (containing a molten iron analogue, sodium) spinning to see if the internal motion of the fluid could set up a magnetic field. This huge laboratory experiment is testament to the efforts being put into understanding how our Earth even generates a magnetic field, let alone why it randomly reverses.
A minority view (which, again is used by doomsayers to link geomagnetic reversal with Planet X) is that there may be some external influence that causes the reversal. You will often see associated with the Planet X/Nibiru claims that should this mystery object encounter the inner Solar System during its highly elliptical orbit, the magnetic field disturbance could upset the internal dynamics of the Earth (and the Sun, possibly generating that “killer” solar flare I discussed back in June). This theory is a poor attempt to link several doomsday scenarios with a common harbinger of doom (i.e. Planet X). There is no reason to think the strong magnetic field of the Earth can be influenced by any external force, let alone a non-existent planet (or was that a brown dwarf?).
The magnetic field strength waxes and wanes… Variations in geomagnetic field in western US since last reversal. The vertical dashed line is the critical value of intensity below which Guyodo and Valet (1999) consider several directional excursions to have occurred.New research into the Earth’s magnetic field was published recently in the September 26th issue of Science, suggesting that the Earth’s magnetic field isn’t as simple as we once believed. In addition to the North-South dipole, there is a weaker magnetic field spread around the planet, probably generated in the outer core of the Earth.
The Earth’s magnetic field is measured to vary in field strength and it is a well known fact that the magnetic field strength is currently experiencing a downward trend. The new research paper, co-authored by geochronologist Brad Singer of the University of Wisconsin, suggests that the weaker magnetic field is critical to geomagnetic reversal. Should the stronger dipole (north-south) field reduce below the magnetic field strength of this usually weaker, distributed field, a geomagnetic reversal is possible.
“The field is not always stable, the convection and the nature of the flow changes, and it can cause the dipole that’s generated to wax and wane in intensity and strength,” Singer said. “When it becomes very weak, it’s less capable of reaching to the surface of the Earth, and what you start to see emerge is this non-axial dipole, the weaker part of the field that’s left over.” Singer’s research group analysed samples of ancient lava from volcanoes in Tahiti and Germany between 500,000 and 700,000 years ago. By looking at an iron-rich mineral called magnetite in the lava, the researchers were able to deduce the direction of the magnetic field.
The spin of the electrons in the mineral is governed by the dominant magnetic field. During times of strong dipolar field, these electrons pointed toward the magnetic North Pole. During times of weak dipolar field, the electrons pointed to wherever the dominant field was, in this case the distributed magnetic field. They think that when the weakened dipolar field drops below a certain threshold, the distributed field pulls the dipolar field off-axis, causing a geomagnetic shift.
“The magnetic field is one of the most fundamental features of the Earth,” Singer said. “But it’s still one of the biggest enigmas in science. Why [the flip] happens is something people have been chasing for more than a hundred years.”
Our meandering magnetic pole The movement of Earth's north magnetic pole across the Canadian arctic, 1831--2001 (Geological Survey of Canada)Although there appears to be a current downward trend in magnetic field strength, the current magnetic field is still considered to be “above average” when compared with the variations measured in recent history. According to researchers at Scripps Institution of Oceanography, San Diego, if the magnetic field continued to decrease at the current trend, the dipolar field would effectively be zero in 500 years time. However, it is more likely that the field strength will simply rebound and increase in strength as it has done over the last several thousand years, continuing with its natural fluctuations.
The positions of the magnetic poles are also known to be wondering over Arctic and Antarctic locations. Take the magnetic north pole for example (pictured left); it has accelerated north over the Canadian plains from 10 km per year in the 20th Century to 40 km per year more recently. It is thought that if the point of magnetic north continues this trend, it will exit North America and enter Siberia in a few decades time. This is not a new phenomenon however. Ever since James Ross’ discovery of the location of the north magnetic pole for the first time in 1831, it’s location has meandered hundreds of miles (even though today’s measurements show some acceleration).
So, no doomsday then?
Geomagnetic reversal is an engrossing area of geophysical research that will continue to occupy physicists and geologists for many years to come. Although the dynamics behind this event are not fully understood, there is absolutely no scientific evidence supporting the claim that there could be a geomagnetic reversal around the time of December 21st, 2012.
Besides, the effects of such a reversal have been totally over-hyped. Should we experience geomagnetic reversal in our lifetimes (which we probably won’t), it is unlikely that we’ll be cooked alive by the Solar Wind, or be wiped out by cosmic rays. It is unlikely that we’ll suffer any mass extinction event (after all, early man, homo erectus, lived through the last geomagnetic shift, apparently with ease). We’ll most likely experience aurorae at all latitudes whilst the dipolar magnetic field settles down to its new, reversed state, and there might be a small increase in energetic particles from space (remember, just because the magnetosphere is weakened, doesn’t mean we wont have magnetic protection), but we’ll still be (largely) protected by our thick atmosphere.
Satellites may malfunction and migrating birds may become confused, but to predict world collapse is a hard pill to swallow.
In conclusion:
Geomagnetic reversal is chaotic in nature. There is no way we can predict it.
Simply because the magnetic field of the Earth is weakening does not mean it is near collapse. Geomagnetic field strength is “above average” if we compare today’s measurements with the last few million years.
The magnetic poles are not set in geographical locations, they move (at varying speeds) and have done ever since measurements began.
There is no evidence to suggest external forcing of internal geomagnetic dynamics of the Earth. Therefore there is no evidence of the solar cycle-geomagnetic shift connection. Don’t get me started on Planet X.
So, do you think there will be a geomagnetic reversal event in 2012? I thought not.
Once again, we find another 2012 doomsday scenario to be flawed in so many ways. There is no doubt that geomagnetic reversal will happen in the future for Earth, but we’re talking about time scales anything from an optimistic (and unlikely) 500 years to millions of years, certainly not in the coming four years…
Sources: NASA, US News, SciVee, How To Survive 2012, AGU
All the particles (excluding their anti-particles) gather for a photo opportunity (Particle Zoo)
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This is a must for any particle physics enthusiast: collect your own particles in the form of a soft, cuddly plushie. From the theoretical Higgs boson to the well known electron, all the quantum particles from the Standard Model can be browsed and chosen for your personal collection. The Particle Zoo is the brain child of Los Angeles-based Julie Peasley, who is making it her duty to give our beloved particles a face and personality. For example: due to his popularity, the Higgs particle is a “bit of a snob” and therefore has a huge smile on his face (after all, wouldn’t you be really smug if everyone wanted to interview you?); the muon (or heavy electron) “lives fast and dies young“; or, hilariously, the unobserved graviton “has big legs for jumping branes.” All the particles have a story and a loving personality. Who would have thought quantum physics could be so much fun?
So that's what the LHC is looking for! Meet the Higgs particle (The Particle Zoo)When I first stumbled across The Particle Zoo website I was in awe of the effort Particle Zookeeper Julie Peasley had put into her creations. On reading the descriptions of each particle’s personalities I realised these fun characters were more than just for entertainment purposes; they were a way to communicate the complex physics behind the quantum world to an audience who didn’t necessarily have a specialist background, but would appeal greatly to physicists too.
“If the particle toys can generate an interest in physics and the subatomic world, I’m grateful. At the very least now all my friends and family know what a boson is,” Julie responded when I asked about the educational uses for these cute creations. Teachers, professors and science educators have ordered whole sets of the particles for use in their physics lessons, proving that The Particle Zoo is not simply ‘just for fun.’
Identifying a face and personality for all the quarks, leptons, bosons, nucleons and theoreticals is not a task to be taken lightly, however. Every characteristic of the professionally-made particles must be likened to their real-world counterpart, thereby ensuring scientific accuracy. If the particle is heavy, it will be filled with something weighty, like gravel (check out the vital statistics for the Higgs boson for example); if it is massless, it is filled with light weight poly fill (such as the photon).
“The particles seem to be catching on more and more. I had a “special” on the Higgs particle all day on September 10 to celebrate the startup. I sold a record amount of particles in a short time. So I am now only $999,999,689 away from buying my own LHC.” – Particle Zookeeper Julie Peasley.
Julie spends some quality time with her Standard Model particles (The Particle Zoo)But there is a lot more to it than matching the physical characteristics of the quanta with the plushie. Julie realised after a compelling lecture by Dr. Lawrence Krauss at UCLA that subatomic particles could have different “personalities” that could be embodied through her talents as an artist (she holds a Fine Arts degree from the University of Colorado) and her lifelong interest in cosmology, the quantum mechanics and theoretical physics. After Krauss’ lecture on The Beginning and End of Time, she hit the textbooks, finding Lisa Randall’s Warped Passages to be a key element to her enthusiasm to giving the particles a face. Each particle has a face that reflects its “personality” – take the neutron with a neutral expression, or the hard-to-detect neutrinos who are all dressed up like little ninjas; every one is designed with a subtle touch.
Select your favourite particle (and don't forget your anti-particles!) (Particle Zoo)In reference to the light-hearted organization, the People for the Ethical Treatment of Hadrons, or simply “PETH” (a group set up to protect the rights of hadrons in particle colliders. After all, how do we know protons don’t feel pain?), Julie said, “I love the idea of hadron’s rights, that is hilarious. Actually, I’m quite jealous of the little hadrons who get to collide at the LHC. They get to go 99.999999% the speed of light. How cool is that?”
Although the LHC has suffered a technical hitch, and the first particle collisions aren’t expected to commence until spring 2009, The Particle Zoo will allow you to explore the quantum world for the time being. I for one have ordered my very own Higgs boson in preparation for my celebrations for when the first particles are collided by the LHC.
“I had a collection of the Giant Microbes toys and thought if people enjoyed those, maybe they would enjoy taking it a step further (well, to be honest, many orders of magnitude further). I honestly had no idea if anyone would be interested but I’m happy to say I’ve gotten over and beyond the positive response I could have imagined.” – Particle Zookeeper Julie Peasley.
So for now, any Higgs boson discovery will fall to Julie’s skilled hands in her “sweatshop of one” until the real force carrier is either proven or disproven in a few months time…
(Warning: Be sure not to leave any anti-particles mingling with the “normal” particles on the same shelf… the resulting annihilation may leave you swamped with fluffy photons…)
Today, CERN announced that the LHCb experiment had revealed the existence of two new baryon subatomic particles. Credit: CERN/LHC/GridPP
[/caption]It’s official, the LHC lawsuit has been dismissed. After seven months of hype, media frenzy and hysteria about the non-existent risk associated with the Large Hadron Collider, Federal Judge Helen Gillmor said her Honolulu court lacked jurisdiction over the European-based CERN particle accelerator. This decision may have been a long-time coming, but at least we can all look forward to spring 2009’s delayed LHC experiments without a fantastical lawsuit hanging over the proceedings.
Although the suit, filed by Walter Wagner and Luis Sancho, was intended to discredit the science and safety behind the LHC, it turns out that it may have done exactly the opposite…
We have been following the LHC lawsuit with some interest on the Universe Today (just in case you hadn’t noticed). At first, the lawsuit seemed to be some kind of half-witted stunt, and it was treated as such. However, once the world realised that two guys in Hawaii really had filed a real lawsuit against the US partners in the European project, the media started to get interested. Questions of concern began to crop up, such as: What if Wagner is right? What if a black hole does swallow Earth after the first particle collisions? What’s going to happen if the LHC does spawn a choking hoard of strangelets?
But as the frenzy calmed and physicists started to formulate their own, more grounded, arguments against the lawsuit’s claims; the public started to investigate what all the fuss was really about. Then we started to get more inquisitive questions, such as: What actually is the Higgs Boson? What is the “Standard Model” and why is it important? What do you mean by “re-create the conditions shortly after the Big Bang”? Very quickly physicists realised that the LHC lawsuit – although clearly unhinged and fearful – could be used to their advantage. Excellent physics speakers such as Brian Cox became the centre of attention as the world’s minds turned to them for answers; the worlds biggest physics experiment suddenly became the topic of conversation in coffee shops and bars the world over.
Actually, this isn’t a bad thing…
Although picking holes in Wagner et al.’s theories was fun for a while, more media hype was on the horizon as the September 10th LHC “switch on” approached. I saw various mainstream media sources publishing horrendous articles predicting the end of the world in days, based purely on the speculative claims of Wagner’s legal action. (After all, fear sells.) However, through the hysteria, many sources were talking coherently and intelligently about what the LHC will do and what we hope to discover. For the first time in many years, a physics experiment was on the front page of every new paper, website and TV headline.
One of the plaintiffs, Luis Sancho, responded to Judge Gillmor’s decision and summed up the lawsuit fairly accurately. “The lawsuit was an unbelievable success in that it put the collider issue on the intellectual agenda,” he said in an email to the New York Times. Although he was referring to his “collider issue”, he is absolutely right that his actions helped to put the LHC on the “intellectual agenda.” For once, it looks like from all this doomsday hype, the LHC managed to generate huge positive interest, and with the patient safety reports and arguments put forward by CERN scientists, any fears were quickly subdued.
Back in the courtroom, Judge Gillmor rightly stated that Wagner’s suit was a “complex debate” of concern to the whole world, and not just physicists. If anything, at least this lawsuit did achieve one thing: it brought a complex physics experiment into the public domain so it could be debated. Plus it created some fantastic advertising ahead of the first (delayed) experiments early next year…
In a statement released by CERN today, due to an obligatory maintenance period, the LHC will have to remain off-line until late March or early April 2009. Problems with an experiment as huge as the worlds biggest particle accelerator can be expected, but this will be a costly delay and a psychological setback after the initial excitement of the first particle circulation on October 10th. The elusive Higgs Boson will have to wait a few more months…
I had a nagging feeling over the weekend after writing about the LHC quench and the two month delay in operations – what if the delay is longer than we think? The severe damage was caused by faulty wiring between two supercooled electromagnets when scientists carried out electrical tests at the facility Friday morning, resulting in a helium leak between sections 3-4 of the 27 km (17 mile) accelerator ring. Although no one was injured, the emergency services had to be called and the electromagnets heated up well beyond operational temperatures. Initial reports suggested experiments would be put back until the end of the year, but now it would seem the LHC won’t accelerate particles again until spring 2009.
“Coming immediately after the very successful start of LHC operation on 10 September, this is undoubtedly a psychological blow. Nevertheless, the success of the LHC’s first operation with beam is testimony to years of painstaking preparation and the skill of the teams involved in building and running CERN’s accelerator complex. I have no doubt that we will overcome this setback with the same degree of rigour and application.” – CERN Director General Robert Aymar.
This is indeed a severe blow to CERN and the scientists at the LHC, but the delay is necessary as the time required to warm up the accelerator, fix the problem and cool it down again will extend into CERN’s obligatory winter maintenance period. Therefore we won’t see any more accelerated protons until 2009.
Once again, in light of these setbacks, physicists are keeping positive and hoping for success in the near future. “The LHC is a very complex instrument, huge in scale and pushing technological limits in many areas,†said Peter Limon in the CERN press release, who was responsible for commissioning the Tevatron at Fermilab in the USA. “Events occur from time to time that temporarily stop operations, for shorter or longer periods, especially during the early phases.”
There have been delays in the commissioning of the LHC (after all, it was originally planned to be operational in the mid-2000s) and setbacks in the last few days, but after two decades of planning and construction, a few more months isn’t that long in the grand scheme of things…
A series of problems forced LHC shutdown (CERN/LHC)
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It’s this sort of news I really did not want to wake up to. At 0927 GMT Friday morning, a fault known as a “quench” resulted in the leakage of a tonne of helium coolant causing 100 of the LHC superconducting magnets to heat up 100°C. The fire services had to be called and it was some time before engineers could access the tunnels to assess the damage. It was worse than they were expecting. Although no one was hurt and there was no danger to the public, the once-supercooled magnets were one hundred times warmer than they should be and optimal vacuum conditions had been lost. To perform repairs, the rest of the damaged sector will need to be warmed up and then slowly cooled down again, resulting in a shutdown of LHC operations for at least two months…
The leak occurred between the Alice and CMS detectors (sectors 3-4) after repairs to the faulty 30-tonne transformer were being finalized and the systems were being powered up to begin a new series of commissioning tests. According to the LHC logbooks, temperatures rose by 100°C and the vacuum required within the equipment for particle circulation to be possible was lost. Engineers had to wait for oxygen levels to return to normal within the tunnels before they could investigate the “meltdown.”
Although last week’s fault with the transformer caused frustration, setting LHC experiments back by a few days, scientists were optimistic the incident would have minimal effect on the first scheduled particle collisions in October. Friday’s quench, however, is a serious incident, knocking the largest experiment mankind has ever attempted offline for at least two months. Although this is sad news, many scientists are keeping a positive attitude:
“This kind of incident was always a possibility with such a unique and demanding project, that’s why we were so tense on the 10th [of September]. Having seen those tantalising first signs of beam in our detectors, everyone is raring to go. So it’s really disappointing, and hard for us to keep in perspective right now. But a delay like this in a 20-year project isn’t an utter disaster and I’m sure the team at Cern will fix it, and make it more robust as they go.” – Prof Jonathan Butterworth of University College London, the UK head of the Atlas detector.
So what happened? The basic operating conditions for the LHC depend on very low temperatures and a very high vacuum state. It would appear both key conditions were lost as engineers tested the electrics of the LHC in the run-up to full commissioning. There was a faulty connection between two of the superconducting magnets, so when the system was switched on, the high current melted the connection, causing the helium leak. The loss of supercooled helium caused a rapid release of stored energy (an event known as a quench), heating the magnets and destabilizing the vacuum conditions.
After such a smooth start to the first proton circulation on September 10th, these setbacks may come as a surprise. However, probing the frontier of physics rarely happens without a few hiccups along the way, so let’s hope this incident will be the last and we can once again look forward to the first particle collisions toward the end of the year…
Artist impression of the Rosetta flyby of Earth. Credit: ESA
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Several different spacecraft have exhibited unexplained changes in speed during gravity assists when flying by Earth. First there was Galileo in 1990 and 1992, NEAR, which flew by Earth in January 1998, and then Cassini in August of 1999. Rosetta — the ESA spacecraft that recently flew by an asteroid – swung by the home planet in March 2005, followed by MESSENGER in August of the same year. All these probes showed an expected change in speed during the flyby. The largest anomaly was recorded for NEAR, whose velocity changed 13 millimeters per second more than it should have. Earlier this year, a group of JPL researchers that had been working on the problem for years basically threw up their hands, saying they hoped other physicists could come up with a solution. They had concluded the anomaly was too large to be explained by known effects related to Einstein’s general theory of relativity. But a new paper proposes that Special Relativity may explain everything.
The speed of the spacecraft is measured by the Doppler shift in radio signals from the spacecraft to the antennas of the Deep Space Network. In a very short and concise paper, (reading it is like watching Will Hunting solve the MIT professor’s equation), Jean Paul Mbelek from CEA-Saclay in France says that the relative motion of the spacecraft and the spinning Earth have not been properly accounted for. When a well known but overlooked effect of Special Relativity is taken into account, where the transverse Doppler effect of the Earth’s spin and the velocity of the craft are factored in, there is no flyby anomaly. “Thus, GR (General Relativity) does not need to be questioned and the flyby anomaly is merely due to an incomplete analysis using conventional physics,” says Mbelek.
flyby-anomaly. credit: arXiv blog
Other explanations had proposed dark matter or “Unruh radiation” could be the answer. But Mbelek says we just haven’t been doing the physics right. He concludes that spacecraft “flybys of heavenly bodies may be viewed as a new test of Special Relativity which has proven to be successful near the Earth.” He proposes a follow-up of tracking the spacecraft trajectories beyond just the probes’ closest approach to Earth to test this hypothesis further.
Debris from particles hitting the collimator blocks were detected in the calorimeters and muon chambers (CERN/LHC/CMS)
[/caption]According to reports, only a day after the first successful circulation of protons in the Large Hadron Collider (LHC) last week, operations at the world’s largest particle accelerator had to be stopped due to a fault with a 30 tonne transformer used to cool part of the facility. The protons were not being accelerated at the time and there was no risk to safety at the LHC.
Rather than maintaining the equipment below the operational 2 Kelvin, the transformer glitch caused temperatures to rise to over 4 Kelvin (which is still cold, after all it is only 4 degrees above absolute zero – but it’s not cold enough). The transformer failed after the successful anticlockwise circulation of protons on the evening of September 11th and rumours about LHC problems have only just been confirmed…
This was bound to be a frustrating problem for the LHC engineers, but in many respects it was inevitable. This is a facility more complex than any technology ever built; a 27 km ring of 1000 supercooled electromagnets, operating at a temperature colder than anything in the Universe, with 2000 separate power supplies and a vast number of synchronized detectors and sensors… it’s little wonder the LHC may experience one or two technical hitches.
“This is arguably the largest machine built by humankind, is incredibly complex, and involves components of varying ages and origins, so I’m not at all surprised to hear of some glitches. It’s a real challenge requiring incredible talent, brain power and coordination to get it running.” – Steve Giddings, physics professor at University of California, Santa Barbara
However, this fault was critical to LHC operations, ultimately shutting the experiment down until technicians find the problem. Judith Jackson, spokesman for the Fermi National Accelerator Laboratory, is not surprised the LHC should suffer the occasional setback. “We know how complex and extraordinary it is to start up one of these machines. No one’s built one of these before and in the process of starting it up there will inevitably be glitches,” she said.
Apparently, transformer malfunctions are commonplace in particle accelerators. “These things happen,” she said. “It’s a little setback and it sounds like they’ve dealt with it and are moving forward.”
According to CERN scientists, the proton beams made “several hundred orbits” clockwise and anticlockwise before the experiment had to shut down.
The Associated Press investigation into the September 11th transformer glitch indicates that the problem has been identified and CERN scientists are still on track for the first particle collisions in October.
