Building BICEP2: A Conversation with Jamie Bock

Caltech Professor of Physics Jamie Bock and his collaborators announced on March 17, 2014 that they have successfully measured a B-mode polarization signal in the cosmic microwave background (CMB) using the BICEP2 telescope at the South Pole. This signal is an important confirmation of key aspects of the theory of cosmic inflation, about how the universe may have behaved in the first fractions of a second of its existence to create the universe we live in today. Inflation was first proposed in 1980 by Alan Guth, a theoretical physicist at the Massachusetts Institute of Technology (MIT), to explain some unusual features of our universe, especially its surprising homogeneity. For all the clumping of stars and galaxies we see in the night sky, the universe seen through the CMB is extremely uniform—so much so that it has been difficult for physicists to believe that the various pieces of the sky were not all in immediate contact with one another at an earlier point in the universe's development.

Since the theory of cosmic inflation was first advanced, most physicists have come to agree that inflation is the best explanation we have for the observable universe. Yet the hope of acquiring direct evidence of inflation was for a long time regarded as a vain one. In 1997, MIT physicist Alan Lightman wrote that since "the extremely rapid cosmic expansion . . . happened so long ago, we will probably never know with certainty whether that event in fact occurred."

And yet now, thanks to a set of bold experiments undertaken with the BICEP telescopes, we seem to be closing in on direct confirmation of the theory of inflation. Bock recently discussed the design of the BICEP instrumentation and how it detected a signal from the dawn of time.

How did the BICEP program begin?

It all started with tennis. In 2001 I played tennis every week with Brian Keating, a Caltech postdoc who is now at UCSD. After a few sets, Brian and I would talk about science for a while. He kept bugging me about doing a CMB polarization experiment that would study structures on degree angular scales—portions of the sky larger than the full moon. Brian was pretty engaged with theoretical astrophysicists, and I liked to design new experiments, so it was a nice combination. Once we got going, our ideas for a new project came together quickly. We knew we were going to need a great team to pull it off, so we wrote a concept proposal that we brought to my colleague at Caltech, the late physicist Andrew Lange. Brian remembers Lange saying, "What you're proposing will cost 10 million dollars . . . but that's okay . . . that's okay!"

The last 13 years have been all about the hard work of designing and running the experiment, building and perfecting the technologies, and analyzing the data. You don't get anywhere in experimental physics without building a team, and what a great team we have! John Kovac came to Caltech as a postdoc shortly thereafter and was a relentless force to organize our team of students, to make sure everything—and I do mean everything—was working as well as it possibly could. Chao-Lin Kuo, also a postdoc at JPL and Caltech, came up with some great ideas, especially new designs to improve the detectors. Both have now gone on to professorships, at Harvard and Stanford, respectively, and are central players in our program. Clem Pryke, now at the University of Minnesota, organized and led the data analysis, a gargantuan task that he's done brilliantly. Our students stepped up to each fill major roles, and the collaboration has been simply amazing. I have never worked with a better group of individuals and am proud to consider myself a member of the team.

What can BICEP see that other telescopes cannot?

BICEP was the first experiment of its kind to go after just the gravitational wave B-modes. This was scientifically risky, because on large degree scales there was no guaranteed signal. It was "B-modes or bust." As a result, we were out in Antarctica running our BICEP instrumentation years before we had any real competition. That has certainly changed now. The field is hypercompetitive! But those first years were really valuable as a learning experience about how to make these difficult measurements.

How does BICEP differ from a traditional large-scale optical or sub-millimeter telescope?

First of all, I should say I love small telescopes. I've done four projects that use small telescopes, each for a unique purpose. Small telescopes have an overlooked capability to gather a lot of light with a wide field of view. This capability keeps on opening doors to new experiments, and especially applications in space where smaller, lighter telescopes are a great advantage. The BICEP telescope is based on a refractor with two lenses. This is not exactly a new idea in optical astronomy; it is similar to Galileo's telescope. But it was a novel approach in CMB measurements and gave us an enormous 20-degree field of view. In fact the light-gathering power of BICEP is not so different from that of the 10-meter telescope looming over us at the South Pole, but BICEP's aperture is just 26 centimeters.

What are the technical challenges involved in looking at a broader rather than a smaller piece of the sky?

To make accurate measurements over a wide area, the challenge is to control false signals. I especially worry about the instrument having a tiny response to the earth, which is a billion times brighter than the signal we want to detect. Our small telescope design works like a champ! We have surrounded the whole telescope with absorbing surfaces cooled to 4 degrees above absolute zero. Then we use an absorbing screen around the primary lens to soak up remaining radiation. Finally, to remove from the system any effects that might arise from having a preferred direction, we spin our telescope around its axis every day. These are things you just can't do with a big telescope.

How is BICEP2 different from the first BICEP instrument, BICEP1?

When the BICEP experiment first began, I was already working on some radical and long-term ideas for building detectors. But it was clearly going to be unrealistic to create completely new detectors while we were also fielding a completely new experiment. So BICEP1 used detectors that were similar to those that Andrew Lange and I developed for the European Space Agency's Planck satellite. These are "spider-web" bolometers. Bolometers are instruments that measure electromagnetic radiation by turning it into heat and measuring the temperature. Spider-web bolometers are made from a fine mesh standing in free space, with just enough material to catch millimeter-wave radiation. These devices that Lange and I developed were made at JPL's Microdevices Laboratory from a micromachined membrane. BICEP1 was a new version of this that we cooked up to detect polarization. But it was designed from the very beginning to accommodate the new technology we were already developing. The new detectors fit right into the telescope.

BICEP2 gets to the same sensitivity as BICEP1 in a tenth of the time. It would have taken BICEP1 30 years to get to where we are with the BICEP2 results that just came out. I really like working at the South Pole, but 30 years? That's a bit much.

How do you achieve this technological improvement?

The name of the game in making a more sensitive CMB polarization experiment is observing with more detectors. But a CMB detector is more than that. It is really a light-gathering, filtering, detection, and readout system. So the challenge is not like going from 35-mm film to a digital chip in your camera, it's like producing the entire camera on a chip. Our approach was basically to make a camera that detects both intensity and polarization via a printed circuit board.

The original inspiration for these ideas came from Caltech physics professor Jonas Zmuidzinas. We feed the detector with an array of little antennas. The radiation goes to a little bolometer at the end of the antenna where it is converted into heat and measured with a superconducting thermometer. Finally multiple detectors are read out together with a superconducting amplifier called a SQUID, developed at the National Institute of Standards and Technology.

Did you expect that BICEP2 would be able to detect B-mode polarization if it were in the CMB?

Honestly, I thought we would continue for decades to drill down to lower and lower levels of signal from the CMB, and never see the B-mode polarization. I was psychologically prepared for that, even expecting it. Our team was becoming increasingly discouraged. Then at a group meeting last March, we saw our first result from BICEP2 showing a B-mode polarization. We reviewed a plot on a projector screen that looked just like the signal we were trying to find, only a lot bigger. There was a sudden transition in the room, from "What on earth are we doing wrong?" to "Maybe this is real!"

For an entire year following this, we debated all the effects that could cause a false signal. There were weeks at a time where we chased a subtle effect that might compromise the data, only to find out that fixing it didn't really make much of a difference. In the end, what finally put us over the top was comparing the BICEP2 maps against the BICEP1 maps, and then against two full years of observations from the new Keck Array experiment at the South Pole, equivalent to an array of five BICEP2 instruments. They all matched.

Over the past months, we gradually became more and more certain that the signal we were seeing was real. It is a strange experience to be going through the activities of daily life, all the while carrying around this gem of knowledge in your head.

How does it feel to be engineering optics that can visualize the remnants of the earliest events in our universe?

It is mind-boggling that we can infer anything about the very instant of the birth of our universe nearly 14 billion years ago. I feel this measurement of the B-mode polarization of the CMB is ahead of its time. The process that produced the polarization involves physics we don't understand, energies beyond the Standard Model, and detecting gravitational waves that were born from quantum fluctuations. I hope this is just the beginning for getting to a real understanding of the exotic physics powering inflation.

But most of all, it is amazing to me that our little band of intrepid scientists, students, postdocs—all of whom I consider colleagues and friends—could build a machine that could actually tell us about the birth of the universe.

Cynthia Eller
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Caltech Appoints Diana Jergovic to Newly Created Position of Vice President for Strategy Implementation

Caltech has named Diana Jergovic as its vice president for strategy implementation. In the newly created position, Jergovic will collaborate closely with the president and provost, and with the division chairs, faculty, and senior leadership on campus and at the Jet Propulsion Laboratory, to execute and integrate Caltech's strategic initiatives and projects and ensure that they complement and support the overall education and research missions of the campus and JPL. This appointment returns the number of vice presidents at the Institute to six.

"Supporting the faculty is Caltech's highest priority," says Edward Stolper, provost and interim president, "and as we pursue complex interdisciplinary and institutional initiatives, we do so with the expectation that they will evolve over a long time horizon. The VP for strategy implementation will help the Institute ensure long-term success for our most important new activities."

In her present role as associate provost for academic and budgetary initiatives at the University of Chicago, Jergovic serves as a liaison between the Office of the Provost and the other academic and administrative offices on campus, and advances campus-wide strategic initiatives. She engages in efforts spanning every university function, including development, major construction, and budgeting, as well as with faculty governance and stewardship matters. Jergovic also serves as chief of staff to University of Chicago provost Thomas F. Rosenbaum, Caltech's president-elect.

"In order to continue Caltech's leadership role and to define new areas of eminence, we will inevitably have to forge new partnerships and collaborations—some internal, some external, some both," Rosenbaum says. "The VP for strategy implementation is intended to provide support for the faculty and faculty leaders in realizing their goals for the most ambitious projects and collaborations, implementing ideas and helping create the structures that make them possible. I was looking for a person who had experience in delivering large-scale projects, understood deeply the culture of a top-tier research university, and could think creatively about a national treasure like JPL."

"My career has evolved in an environment where faculty governance is paramount," Jergovic says. "Over the years, I have cultivated a collaborative approach working alongside a very dedicated faculty leadership. My hope is to bring this experience to Caltech and to integrate it into the existing leadership team in a manner that simultaneously leverages my strengths and allows us together to ensure that the Institute continues to flourish, to retain its position as the world's leading research university, and to retain its recognition as such."

Prior to her position as associate provost, Jergovic was the University of Chicago's assistant vice president for research and education, responsible for the financial management and oversight of all administrative aspects of the Office of the Vice President for Research and Argonne National Laboratory. She engaged in research-related programmatic planning with a special emphasis on the interface between the university and Argonne National Laboratory. This ranged from the development of the university's Science and Technology Outreach and Mentoring Program (STOMP), a weekly outreach program administered by university faculty, staff, and students in low-income neighborhood schools on the South Side of Chicago, to extensive responsibilities with the university's successful bid to retain management of Argonne National Laboratory.

From 1994 to 2001, Jergovic was a research scientist with the university-affiliated National Opinion Research Center (NORC) and, in 2001, served as project director for NORC's Florida Ballot Project, an initiative that examined, classified, and created an archive of the markings on Florida's 175,000 uncertified ballots from its contested 2000 presidential election.

Jergovic earned a BS in psychology and an MA and PhD in developmental psychology, all from Loyola University Chicago, and an MBA from the Booth School of Business at the University of Chicago.

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Monday, March 31, 2014
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Theoretical Physicist Wins Feynman Prize for Excellence in Teaching

Steven C. Frautschi, professor of theoretical physics, emeritus, at Caltech, has been awarded the Richard P. Feynman Prize for Excellence in Teaching—Caltech's most prestigious teaching honor.

Named after Caltech physicist Richard P. Feynman, the prize is awarded annually to a Caltech professor "who demonstrates, in the broadest sense, unusual ability, creativity, and innovation in undergraduate and graduate classroom or laboratory teaching."

This is the first time the Feynman Prize has been awarded to an emeritus faculty member and also the first time it has been awarded to a teaching assistant.

Frautschi has won three ASCIT (Associated Students of the California Institute of Technology) teaching awards during his time at Caltech. Since his retirement from full-time teaching in 2006, Frautschi has continued on at Caltech as a teaching assistant for the freshman Physics 1 class in classical mechanics and electromagnetism. As Frautschi explains, "There is a long tradition of having at least some of the sections in freshman physics taught by Caltech professors. I've just stepped into that tradition. I love the material in basic physics and how it affects so many things in the world around us, and I like the continued contact with young people very much."

Caltech students are as enthusiastic about Professor Frautschi as he is about teaching. Frautschi is credited by several students with pulling them through physics when they thought they would fail. Students describe Frautschi as "amazing," "awesome," and "beyond helpful." They enjoy his "use of uncommon real-world examples" along with his "awesome Converse shoes," and they say "learning from him is a blast." Others go even further. A biology major confesses, "I used to absolutely hate physics because I thought it was too difficult and useless, but Frautschi really clarified my understanding and sparked my interest in physics." Now, says this student, "I wouldn't be opposed to being a physics major solely because of him." Another student says simply, "I want to be like Professor Frautschi when I grow up."

Those are big shoes to fill. Frautschi, raised in Wisconsin, matriculated at Harvard when he was only 16 years old. "I had a wonderful time at Harvard," says Frautschi. "To me it was like a large cookie jar full of wonderful goodies to dip into." He studied physics and math there but has fond memories of auditing classes in art history and geology as well. After college, Frautschi won a Harvard fellowship to spend a year traveling through the Near East and Europe, where he enjoyed "a great many operas among other things." Graduate school followed at Stanford University, where Frautschi concluded that theory, rather than experiment, would be his forte in physics. After Stanford, Frautschi pursued postdoctoral fellowships at the Hideki Yukawa Institute for Theoretical Physics in Kyoto and at UC Berkeley.

Frautschi's eventual move to Caltech was initiated when Murray Gell-Mann (later a Nobel Prize winner and now the Robert Andrews Millikan Professor of Theoretical Physics, Emeritus) visited Berkeley in 1961, just as Frautschi's postdoctoral work on strongly interacting particles was concluding. As Frautschi remembers it, "One evening at home, I got a phone call from one of the other postdocs. He said, 'You must come to the radiation laboratory tomorrow, because Gell-Mann is asking questions, and we can't answer them.'" Fortunately, Frautschi had been considering the problems Gell-Mann asked about, and the two ended up collaborating while Frautschi began an assistant professorship at Cornell University. Within the year, Frautschi was invited to join the faculty at Caltech.

"At that time, Feynman and Gell-Mann were active, and there were wonderful students also, so coming to Caltech was a very attractive opportunity," says Frautschi. Frautschi actually knew the prize's namesake personally and had the opportunity to watch him teach. Frautschi remembers attending a graduate course Feynman taught on the quantum theory of gravity during the 1960s; he also remembers Feynman's "famous sessions with the undergrads, where he would entertain any question whatsoever. This was utterly remarkable to me. I've never heard of another professor who did this. The students regarded Feynman as their patron saint at Caltech, and the reputation is quite deserved."

Frautschi's reputation as a teacher is equally well deserved. In addition to his current work as a teaching assistant and his regular teaching commitments over the years, Frautschi participated in Caltech's 52-episode television course The Mechanical Universe, prepared in the 1980s by David Goodstein, the Frank J. Gilloon Distinguished Teaching and Service Professor, Emeritus. Frautschi is lead author of the textbook of the same title that is still in use today for freshman physics courses at Caltech.

Frautschi's love of opera, discovered while traveling in Europe in his early 20s, was another experience he shared with his students at Caltech, especially during his tenure as Master of Student Houses from 1997 to 2002. "With a boost from Beverly Sills in New York, it had become standard to put supertitles above the stage during the opera so that you could actually follow what's going on, line by line. I thought we'd get just a few students the first time I set up a trip to the opera," says Frautschi, "but we've had up to 40 at times." Since the construction of Walt Disney Concert Hall, Frautschi takes it upon himself to regularly escort Caltech students to concerts there.

Frautschi and his wife, Mie, are both music lovers, and they raised two daughters who became professional violinists. They purchased a condo in Aspen, Colorado, at first to be near the Aspen Center for Physics, and later for their daughters to be near the Aspen Music Festival. They have since donated their condo to Caltech to fund rehearsal space for Caltech's band and orchestra on the second floor of the Winnett Center as part of the larger renovation project for this building.

As the official citation for the Feynman Prize states, "anyone familiar with Steven knows his recent work in Physics 1 is just the latest stage" in what has been a long history of "passion for teaching and service to student life. He set these priorities long ago and has maintained a level of focus and energy that is astonishing."

The Feynman Prize has been endowed through the generosity of Ione and Robert E. Paradise and an anonymous local couple. Some of the most recent winners of the Feynman Prize include Paul Asimow, professor of geology and geochemistry; Morgan Kousser, the William R. Kenan, Jr., Professor of History and Social Science; and Dennis Dougherty, the George Grant Hoag Professor of Chemistry.

Nominations for next year's Feynman Prize for Excellence in Teaching will be solicited in the fall.  Further information about the prize can be found on the Provost's Office website.

Cynthia Eller
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NuSTAR Reveals Radioactive Matter in Supernova Remnant

New details suggest how massive stars explode

Using its X-ray vision to observe what is left of a massive star that exploded long ago, NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) spacecraft has shed new light on an old question: How exactly do stars go out with such a bang? For the first time, NuSTAR has mapped radioactive material from the core of such a supernova explosion. The results suggest that the core of the star actually sloshes around before shock waves rip it apart.

Between August 2012 and June 2013, NuSTAR trained its eyes multiple times on the Cassiopeia A (Cas A) remnant—the leftovers of a star that collapsed and exploded more than 11,000 years ago. With the observatory's sensitivity to high-energy X-rays, it was able to image and then map the distribution in Cas A of radioactive titanium-44, an atom produced at the core of the exploding star. Members of the NuSTAR team report the observations in the February 20 issue of the journal Nature.

"We are excited about these new results. Probing supernova explosions is one of the things that NuSTAR was specifically designed to do," says Fiona Harrison, the Benjamin M. Rosen Professor of Physics and Astronomy at Caltech and NuSTAR's principal investigator. "NuSTAR is the only spacecraft currently capable of making the measurements that led to these new insights."

Although other powerful X-ray telescopes, such as NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton, have imaged the Cas A remnant before, those observatories can only detect material that has been heated by the explosion. NuSTAR's specially coated optics and newly developed detectors allow it to image at higher energies. So what is particularly exciting about the NuSTAR map is that it shows all of the titanium-44, revealing both the heated and unheated material from the heart of the explosion.

"With NuSTAR we have a new forensic tool to investigate the explosion," says Brian Grefenstette, lead author of the paper, also from Caltech. "Previously, it was hard to interpret what was going on in Cas A because the material that we could see only glows in X-rays when it's heated up. Now that we can see the radioactive material, which glows in X-rays no matter what, we are getting a more complete picture of the core of the explosion."

 NuSTAR has provided the first observational evidence in support of a theory that says exploding stars slosh around before detonating. That theory, referred to as mild asymmetries, is shown here in a simulation by Christian Ott, professor of theoretical astrophysics at Caltech.

The distribution of titanium-44 that NuSTAR observed suggests that supernova explosions of Cas A's kind are not completely symmetric, nor are they driven by powerful jets, as some had hypothesized. Instead, computer simulations that match the NuSTAR data suggest that stars like Cas A slosh around before exploding and therefore disperse the radioactive material at their cores in a mildly asymmetric way.

"When we try to recreate supernovas with spherical models, the shock wave from the initial collapse of the star's core stalls out," explains Harrison. "Our new results point to strong distortions of a spherical shape as key to the process of reenergizing the blast wave. The exploding star literally sloshes around before detonating."

As revealing as the NuSTAR findings are, they have also created a new mystery for scientists to ponder. Since both the iron and titanium in the remnant originated in the star's core, the researchers had expected to find significant overlap between the titanium-44 map and a previous map based on Chandra's observations of iron in the remnant. Instead, the two did not match up well. So, the researchers say, the case of the Cas A remnant is far from closed.

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory (JPL) for NASA's Science Mission Directorate in Washington. Along with Harrison and Grefenstette, additional Caltech coauthors on the paper, "Mapping Cassiopeia A in Radioactive 44Ti: Probing the Explosion's Engine," are Kristin Madsen, Hiromasa Miyasaka, Vikram Rana, and JPL researcher Daniel Stern.

Kimm Fesenmaier
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Caltech Physicists Win Sloan Research Fellowships

Three Caltech assistant professors are among the 126 early-career scientists awarded 2014 Sloan Research Fellowships by the Alfred P. Sloan Foundation. Clifford Cheung, assistant professor of theoretical physics, Philip Hopkins, assistant professor of theoretical astrophysics, and David Hsieh, assistant professor of physics, each will receive $50,000 from the Sloan Foundation to further their research. The recipients are selected based on their research accomplishments, creativity, and potential to become leaders in their respective fields.

Cheung, a member of the Caltech Particle Theory Group, received his PhD from Harvard University in 2009 and joined the Caltech faculty in 2012. Caltech professor of physics and former executive officer for physics Kenneth G. Libbrecht says he expects Cheung to assume a leadership role in the theoretical particle physics field as new discoveries at the Large Hadron Collider and other facilities "cause scientists to revise their current understanding of the laws of nature at the most fundamental level."

Phillip Hopkins received his PhD from Harvard in 2008 and became a member of the Caltech faculty in 2013. A theoretical and computational astrophysicist, Hopkins studies the formation and evolution of galaxies, stars, and supermassive black holes throughout the universe. According to Caltech professor of theoretical astrophysics and executive officer for astronomy E. Sterl Phinney, Hopkins has a "unique ability to synthesize vast quantities of complicated observational data, identify physical and computational models that will improve our understanding of that data, and communicate this to the world in a way that inspires further investigation."

David Hsieh received his PhD from Princeton University in 2009 and joined the Caltech faculty in 2012. Hsieh's research focuses on spectroscopic investigations of topologically ordered electronic systems. According to Libbrecht, Hsieh is well-known in the physics research community for his expertise in angle-resolved photo-emission spectroscopy measurements. "He is clearly a gifted experimental physicist, and he seems destined to become a central figure in the emerging study of 3-D topological materials."

"Caltech has a well-established reputation for excellence in physics research and education," says B. Thomas Soifer, professor of physics and chair of Caltech's Division of Physics, Mathematics and Astronomy. "The fact that three early-career Caltech physicists were chosen to receive Sloan Research Fellowships for 2014 is a sign of the Institute's strength in this area, and it shows great promise for the future."

Each year the Sloan Foundation awards fellowships to researchers in eight scientific and technical fields: chemistry, computer science, economics, mathematics, evolutionary and computational molecular biology, neuroscience, ocean sciences, and physics.

Brian Bell
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Monday, April 7, 2014
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Wednesday, April 23, 2014
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The Art of Scientific Presentations

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Juggling Teaching at a Community College and Research at Caltech

NOvA Sees First Long-distance Neutrinos

The NOvA experiment, centered at the Department of Energy's Fermi National Accelerator Laboratory (Fermilab) near Chicago has detected its first neutrinos.

Ryan Patterson, assistant professor of physics at Caltech and principal investigator for the Caltech NOvA team of eight researchers, states, "With these first neutrinos in hand, we celebrate the official start of our physics run. The data we collect with NOvA will provide a brand-new window on how neutrino masses arise and relate to one another, and whether there are new physical laws lurking in the neutrino sector of the standard model of particle physics."

Neutrinos are curious particles that travel near the speed of light, rarely interacting with matter. The NOvA experiment, a collaboration of 208 scientists from 38 institutions, is scheduled to run for six years. It includes the Fermilab accelerator and two receivers, one located near Fermilab, the other some 500 miles away in Ash River, Minnesota, near the Canadian border.

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