Wednesday, April 25, 2012

Approximations

Can't help it... this must be shared!

Monday, April 23, 2012

It's About Time

I've just recently completed Adam Frank's About Time, and while I intended to write a full review, instead I feel that I must share with you two important stories recounted within its pages.

I will say this: I found the book a fascinating, enjoyable and well-researched read. I was disappointed to see no mention of some of the newest cosmological theories, which, as they include information theory (the entropy of a black hole being connected with how many bits of information it has inhaled, for instance), seem inextricably connected to the current cultural zeitgeist - the basic thesis of the entire book being the "braiding of science and culture." But it's no great loss. There is plenty already.

The two stories I wanted to share begin with Georges Lemaitre. Lemaitre was an astronomer and physicist, the first to suggest a "Big Bang" (expansion) model for the universe, but also a Catholic priest. Lemaitre was thus more-than-averagely equipped to understand the connections between science and religion, and the dangerous weight that they could impress on one another. When Lemaitre learned in 1951 that Pope Pius XII gave full endorsement of the Big Bang cosmological model (as presented in the combined work of Lemaitre himself, Gamow, Alpher and others), his response is telling: he was "horrified." The pope proclaimed to the Pontifical Academy of Sciences that "present-day science... has succeeded in bearing witness to the august instant of the primordial Fiat Lux.... Hence, creation took place.... Therefore God exists."
Lemaitre, understanding that any scientific hypothesis could be overturned if the data disagreed, traveled to Rome and "counseled the pope against linking the faith to any contingent scientific hypothesis" [pg 202]. Both science and religion were important to Lemaitre - so important, in fact, that he would not allow either one to direct or support the other. There's something to be learned here, even if the fans of Intelligent Design (and, in ironic fact, those vehemently opposed to ID) refuse to learn it.

The second story is about homeland security - long before the term "homeland security" existed. In the early 80's when Reagan was president, a burgeoning network of Earth-orbiting GPS satellites was finally coming into its own. More satellites were being launched throughout the 80's, but, at the time, GPS technology was limited to those with a security clearance: before 1983, GPS was entirely a classified military effort. But what happened next should be a lesson in how to correctly deal with international threats.
On September 1st, 1983, Korean Air flight 007, on the final leg of its journey from New York to Seoul, veered off course and strayed into Soviet airspace. Crossing over the Kamchatka Peninsula, the passenger plane was shot down by two Soviet fighter jets. All 263 passengers aboard were killed, including a US Senator. Reagan responded first with horror and outrage at the Soviets, but then did something which seems almost the opposite of his Republican legacy George W: he declassified GPS [pg 240]. Instead of responding to the perceived Soviet threat by tightening the leash on "secure" information (such as we do now, after 9/11), he made it openly and publicly available. And now, the Cold War is over and GPS is one of the most successful technologies out there. Perhaps we could learn by example and try opening up our files on nuclear energy.

I leave you with this thought from the book.
Rather than make claims of final theories, perhaps we should focus on our ever-continuing dialogue with the universe. It is the dialogue that matters, not its imagined end. It is the sacred act of inquiry wherein we gently trace the experienced outlines of an ever-greater whole. It is the dialogue that lets the brilliance of the diamond's infinite facets shine clearly. It is the dialogue that instills within us a power and capacity that is, and always has been, saturated with meaning.... With each step we gain a deeper sense of the awe and beauty that suffuse the universe's essential mystery.

Friday, April 20, 2012

"Fireballs" Snuffed

ResearchBlogging.org





This post was chosen as an Editor's Selection for ResearchBlogging.org


(check it out! Editor's Pick on ResearchBlogging.org!)



Ok, I admit, the title is a bit misleading. That's journalism, right?
So the story begins thusly: somewhere out there in the universe, something is producing really high energy cosmic rays. I mean, really high energy. Energies above 10^18 electronvolts (that's a one followed by eighteen zeros). That's nearly a million times more energetic than the LHC upgrade. Boggles-the-mind high energy.
We've detected those high energy cosmic rays here on Earth. And we want to know where they come from.
There aren't many things we know of in the universe that are powerful enough to produce such high-energy cosmic rays. Neutron star mergers, perhaps. Supernova explosions. But gamma-ray bursts (GRBs) seemed like a really good candidate. These astrophysical explosions are tremendously energetic, and so, it was proposed, they could be producing the seriously high energy cosmic rays we've been seeing. But the IceCube collaboration published results this week that seem to indicate "no such luck."
In the fireball model of the physics taking place inside a gamma-ray burst, the production of the high-energy cosmic rays is accompanied by a flux of neutrinos. The number of neutrinos produced is related to the number of proton-photon interactions inside the GRB, and this is in turn related to the energetic cosmic rays produced (the cosmic rays observed are generally protons or neutrons). So if the model was correct, and GRBs are the source of the cosmic rays, then each cosmic ray event should be associated with a flux of neutrinos, coming from the same location in the sky and at a specified time and energy. And IceCube set out to look for just that.
The IceCube detector is itself a wonder of the universe (in my opinion, anyway!). Strings of sensitive electronics extend down into the polar ice cap over Antarctica to a depth of one and a half miles. These detectors look for the tiny flashes of blue light produced when a neutrino interacts with the ice. It doesn't happen very often - neutrinos are notoriously hard to detect, because they don't like to interact with matter all that much - but when you have a cubic kilometer of ice to work with, you're bound to see something!
That's where the results come in. The IceCube collaboration saw... nothing. No flux of neutrinos from gamma-ray bursts. In fact, they saw so much nothing that they were able to put an upper limit on the number of possible neutrinos that was nearly a factor of four lower than what the fireball models suggested. So either the fireball models are (at least partially) incorrect, or gamma-ray bursts are not the source of the high energy cosmic rays.
Something to keep in mind: scientists appreciate a negative result just as much as a positive one. Not seeing what you expected to see is still just as important (perhaps more so) than seeing what you expected to see. It means you have to go back to the drawing board, think through everything again, and potentially come up with a brand new model to explain what you did see.
As the authors of the study themselves say, "all such models - in which all extragalactic cosmic rays
are emitted from GRBs as neutrons - are now largely ruled out.... either the proton density in GRB fireballs is substantially below the level required to explain the highest-energy cosmic rays or the physics in GRB shocks is significantly different from that included in current models. In either case, our current theories of cosmic-ray and neutrino production in GRBs will need to be revisited."

Reference:
Abbasi, R., Abdou, Y., Abu-Zayyad, T., Ackermann, M., Adams, J., Aguilar, J., Ahlers, M., Altmann, D., Andeen, K., Auffenberg, J., Bai, X., Baker, M., Barwick, S., Bay, R., Bazo Alba, J., Beattie, K., Beatty, J., Bechet, S., Becker, J., Becker, K., Bell, M., Benabderrahmane, M., BenZvi, S., Berdermann, J., Berghaus, P., Berley, D., Bernardini, E., Bertrand, D., Besson, D., Bindig, D., Bissok, M., Blaufuss, E., Blumenthal, J., Boersma, D., Bohm, C., Bose, D., Böser, S., Botner, O., Brayeur, L., Brown, A., Buitink, S., Caballero-Mora, K., Carson, M., Casier, M., Chirkin, D., Christy, B., Clevermann, F., Cohen, S., Colnard, C., Cowen, D., Cruz Silva, A., D’Agostino, M., Danninger, M., Daughhetee, J., Davis, J., De Clercq, C., Degner, T., Descamps, F., Desiati, P., de Vries-Uiterweerd, G., DeYoung, T., Díaz-Vélez, J., Dierckxsens, M., Dreyer, J., Dumm, J., Dunkman, M., Eisch, J., Ellsworth, R., Engdegård, O., Euler, S., Evenson, P., Fadiran, O., Fazely, A., Fedynitch, A., Feintzeig, J., Feusels, T., Filimonov, K., Finley, C., Fischer-Wasels, T., Flis, S., Franckowiak, A., Franke, R., Gaisser, T., Gallagher, J., Gerhardt, L., Gladstone, L., Glüsenkamp, T., Goldschmidt, A., Goodman, J., Góra, D., Grant, D., Griesel, T., Groß, A., Grullon, S., Gurtner, M., Ha, C., Haj Ismail, A., Hallgren, A., Halzen, F., Han, K., Hanson, K., Heereman, D., Heinen, D., Helbing, K., Hellauer, R., Hickford, S., Hill, G., Hoffman, K., Hoffmann, B., Homeier, A., Hoshina, K., Huelsnitz, W., Hülβ, J., Hulth, P., Hultqvist, K., Hussain, S., Ishihara, A., Jacobi, E., Jacobsen, J., Japaridze, G., Johansson, H., Kappes, A., Karg, T., Karle, A., Kiryluk, J., Kislat, F., Klein, S., Köhne, J., Kohnen, G., Kolanoski, H., Köpke, L., Kopper, S., Koskinen, D., Kowalski, M., Kowarik, T., Krasberg, M., Kroll, G., Kunnen, J., Kurahashi, N., Kuwabara, T., Labare, M., Laihem, K., Landsman, H., Larson, M., Lauer, R., Lünemann, J., Madsen, J., Marotta, A., Maruyama, R., Mase, K., Matis, H., Meagher, K., Merck, M., Mészáros, P., Meures, T., Miarecki, S., Middell, E., Milke, N., Miller, J., Montaruli, T., Morse, R., Movit, S., Nahnhauer, R., Nam, J., Naumann, U., Nowicki, S., Nygren, D., Odrowski, S., Olivas, A., Olivo, M., O’Murchadha, A., Panknin, S., Paul, L., Pérez de los Heros, C., Piegsa, A., Pieloth, D., Posselt, J., Price, P., Przybylski, G., Rawlins, K., Redl, P., Resconi, E., Rhode, W., Ribordy, M., Richman, M., Riedel, B., Rizzo, A., Rodrigues, J., Rothmaier, F., Rott, C., Ruhe, T., Rutledge, D., Ruzybayev, B., Ryckbosch, D., Sander, H., Santander, M., Sarkar, S., Schatto, K., Schmidt, T., Schöneberg, S., Schönwald, A., Schukraft, A., Schulte, L., Schultes, A., Schulz, O., Schunck, M., Seckel, D., Semburg, B., Seo, S., Sestayo, Y., Seunarine, S., Silvestri, A., Smith, M., Spiczak, G., Spiering, C., Stamatikos, M., Stanev, T., Stezelberger, T., Stokstad, R., Stößl, A., Strahler, E., Ström, R., Stüer, M., Sullivan, G., Taavola, H., Taboada, I., Tamburro, A., Ter-Antonyan, S., Tilav, S., Toale, P., Toscano, S., Tosi, D., van Eijndhoven, N., Van Overloop, A., van Santen, J., Vehring, M., Voge, M., Walck, C., Waldenmaier, T., Wallraff, M., Walter, M., Wasserman, R., Weaver, C., Wendt, C., Westerhoff, S., Whitehorn, N., Wiebe, K., Wiebusch, C., Williams, D., Wischnewski, R., Wissing, H., Wolf, M., Wood, T., Woschnagg, K., Xu, C., Xu, D., Xu, X., Yanez, J., Yodh, G., Yoshida, S., Zarzhitsky, P., & Zoll, M. (2012). An absence of neutrinos associated with cosmic-ray acceleration in γ-ray bursts Nature, 484 (7394), 351-354 DOI: 10.1038/nature11068

Wednesday, April 18, 2012

Long Live Holifield

Here is the news release from ORNL regarding the HRIBF closure. I haven't altered it in any way (even leaving the errors in the spelling of a good friend's name). Original link is here.



With experiments right to the finish, Holifield Facility user program closes

The Holifield Radioactive Ion Beam Facility ran experiments right up to the midnight, April 15, end of user operations.
(hi-res image)

The Holifield Radioactive Ion Beam Facility user program has ended in style, with researchers scurrying to complete three exciting experiments before program’s last day of user operations on April 15. The final day was initially scheduled for April 1, but the user program received a two-week “reprieve” to finish the three experiments.

Approximately 40 people — researchers, users and Holifield veterans — showed up to count down the last minutes of beam time at midnight, Sunday, April 15.

The facility will now go into “warm standby,” says Physics Division Director David Dean.

Slightly less than a month before the user operations ended, the Holifield Facility marked its 50th anniversary. March 18, 1962, was the day operators for the Oak Ridge Isochronous Cyclotron, the “front end” of the radioactive ion beam source, circulated its first light ion beam.

The ensuing half-century has produced volumes of research through beams of, initially, heavy ions and, later, short-lived, radioactive nuclei. The Holifield Facility has been the experimental resource and training ground for researchers located all across the low-energy physics scientific community, from all corners of the world.

The three final user experiments are typical of what the facility has offered the research community for all these years.

Ricardo Orlandi, a researcher from CSIC Madrid, is leading a measurement of a unique reaction on Tin-132, an unstable isotope important to nuclear astrophysicists who investigate how the heaviest elements are created in supernova explosions. It is also important to researchers investigating the structure of the unstable, ‘doubly magic’ tin isotope, which has closed shells of both protons and neutrons.

Another experiment, led by ORNL physicist Krzysztof Rykaczewski, is using the facility’s first laser ion source and new second radioactive ion beam platform to collect data on exotic isotopes of gallium. The laser source, built by ORNL’s Yuan Liu, coupled to the facility’s isobar separator, provided completely pure beams for study of the structure of these rare isotopes. At the same time, Rykaczewski is commissioning the neutron detector 3Hen, which could see future service at another isotope facility. The HRIBF experiment hopes to yield lifetime and level information on gallium-86; previously, only the existence of this isotope had been reported.

The third project is actually four experiments to study different states of a variety of exotic tin isotopes. ORNL staff members Robert Varner and Jim Beene, working with postdoc Mitch Allmond and the University of Tennessee’s Kate Jones and Anissa Bey, blasted a beryllium-9 target with unstable tin-126, 128, 130, and 132 nuclei, and detected the resulting light particles and gamma rays to probe tin isotopes with one additional neutron to the beam. These measurements are important both to learn about the structure of heavy exotic nuclei and about supernova element creation. Two of these experiments, on tin-126 and 128, will be part of the thesis work of graduate student Brett Manning from Rutgers University.

The Holifield Facility has offered nuclear theorists and astrophysicists unique beams for studies of the forces that hold protons and neutrons together into an atomic nucleus. ORIC, which produces the initial light ion beam, was one of the first isochronous cyclotrons of its kind. Holifield is the only facility in the world that produces unique, short-lived beams of both proton-rich and neutron-rich beams such as Fluorine-17.

Besides the one-of-a-kind beams the HRIBF produced, the facility was unique in itself: For example, the massive doors that shield the staff from the cyclotron were the largest the supplying safe company had ever produced. The 100-foot-tall electrostatic tandem accelerator — the silo-shaped Lab landmark — has generated an electrostatic voltage of 32 million volts, which might still hold the record for the highest voltage ever produced by a man-made device.

The stream of researchers who came to ORNL inspired the establishment in 1982 of ORNL’s initial collaboration with state of Tennessee universities — the Joint Institute for Heavy Ion Research, located near the Holifield Facility.

The end of the Holifield Facility’s user program was announced in the February 2011 budget request for Fiscal Year 2012. The cost-saving measure was coupled with the end of another, much larger physics facility’s mission, Fermilab’s Tevatron, whose mission has been supplanted by Europe’s Large Hadron Collider.

The Holifield Facility itself more than doubled its own initial life expectancy in the early 1990s, when the late researchers Russell Robinson and Jerry Garrett led the conversion of the heavy ion facility to a radioactive ion Beam facility where beams produced from the bombardment of targets with intense light ions from ORIC were accelerated in the tall tandem.

The warm standby status conferred upon the facility may or may not be permanent. Other missions for the Holifield Facility are under consideration. The break, in fact, provides a needed two-month maintenance period for the tandem accelerator.

“We’re hoping we can get approval to run some experiments on the tandem, which is relatively cheap to run,” says the Physics Division’s Michael Smith, whose nearly two-decade ORNL tenure in astrophysics has been based at Holifield. “We hope to carry out forefront measurements as well as commission new detector and target systems for use in next-generation facilities.”

In the meantime, the last flurry of radioactive ion beam experiments recalls a half-century of science produced by a unique, at times quirky, but resilient workhorse.

“It’s been hectic and exciting,” Michael says. “We’ve had all these different groups in the facility simultaneously doing different experiments. A new laser ion source, new platform, new detector system, new reactions, and a lot of exotic beams that can’t be done anywhere else in the world. It’s an incredibly productive way to do science.”— Bill Cabage, April 17, 2012

Sunday, April 15, 2012

The End

Under three hours to go now. People are beginning to appear, milling around in an anxious, fidgeting kind of anticipation, waiting for an event no one as yet comprehends. The HRIBF ceases operation at midnight Eastern Daylight Time tonight. And when it does, we will be here.

Nobody quite knows what to expect. Will DOE call us and tell us when to pull the plug? Do we get to sneak a few last minutes in because our clock isn't synced with an official time server? Will someone give a speech, or sing a dirge, or lock themselves in the ORIC vault? Will anyone cry?

There's a countdown clock running on the large monitor in the control room, where the operators sit and tweak the beam current slowly upward, knowing that it really doesn't matter anymore if something breaks. Two and a half hours now.

It's so unbearably sad.

Friday, April 13, 2012

Stardust Science

Well, folks... here it is. My tribute to the Holifield Radioactive Ion Beam Facility, which closes its doors on this coming Sunday, April 15th. I put a lot of effort into this - I hope it means something to you, as it does to me.