SCIPP Seminars





Last updated:03/31/09

Tuesday March 31st, 10:30am
Marco Battaglia (LBNL-UCB-CERN)
Monolithic Si Pixel Sensors from Future Particle Colliders to Fast Nano-Imaging
Particle physics at future colliders and multi-scale imaging share much in terms of requirements for new position sensitive detectors: small pixels, radiation-tolerant cells, minimum thickness and fast readout. The talk will discuss these requirements together with the R&D path to develop monolithic Si pixel sensors for e+e- linear colliders and export instrumentation and reconstruction techniques to applications in electron microscopy, beam diagnostics and dose deposition assessment in hadrontheraphy.
Thursday March 26th, 10:30am
Cary Zeitlin (Southwest Research Institute)
Thursday March 26th, 10:30am
Cosmic Rays and Humans in Space

Humans in space, particularly on long-duration missions, encounter a unique health risk not experienced in any other setting: a low-rate, chronic radiation dose that includes a significant contribution from heavy ions. Outside low-Earth orbit, the two main sources of these particles are Galactic Cosmic Rays and Solar Particle Events. The latter can generally be mitigated by shielding, but the GCR present a less tractable problem. In order to manage the risks arising from these exposures, an accurate model of heavy ion transport is needed. Accurate transport calculations depend critically on nuclear fragmentation cross sections, relatively few of which have been measured. A program to measure many of cross sections using a simple table-top experiment will be described. Pertinent flight measurements and instruments are also described, including the Radiation Assessment Detector (RAD) which will fly on the Mars Science Laboratory (MSL). RAD for MSL is a sophisticated, extremely compact and lightweight charged particle spectrometer with the additional ability to measure neutrons from about 10 to 100 MeV. The neutron capability is expected to be greatly enhanced in a next-generation RAD to be built for crew dosimetry aboard the International Space Station.

Tuesday March 24th, 10:30am
Marcus Ziegler (UCSC-SCIPP)
New Tracking Detectors for High Energy (Astro) Physics
Less than a year after its launch, the Fermi Gamma-Ray Space Telescope is already giving us a whole new view of the gamma-ray sky. In this talk I will describe the challenges in the detector design that had to be overcome and point out the differences with collider-based tracking detectors. I will present some highlights in the field of pulsar astrophysics recently achieved with Fermi, focusing on the search for radio-quiet pulsars. These recent results provide a better understanding of the high-energy emission from pulsars. I will also discuss how future polarization measurements can provide a deeper insight into the cosmic acceleration mechanisms. Recent studies have demonstrated that efficient polarimetry can be achieved by making use of photo absorption and reconstructing the event in a GEM-based TPC (Time Projection Chamber) that is read out with a pixelated detector. I will discuss this and other applications of GEM-based detectors.
Thursday March 19th, 10:30am
Sven Vahsen (LBNL)
"Exploring the TeV Scale  with Pixel Detectors "
As present and future particle colliders confront the TeV scale, we
expect to reveal the mechanism of electroweak symmetry breaking, and
hope to produce new particles - possibly even WIMP dark matter - in
the laboratory for the first time. I will start out by motivating why
the important measurements at the TeV scale demand precision tracking,
and why this in turn requires pixels.

I will then discuss in detail two pixel-based detectors:

The ATLAS Pixel Detector is currently being commissioned at CERN. It
faces the unprecedented challenge of performing pattern recognition
and vertex reconstruction in the harsh environment just outside the
LHC beampipe. I will review how the detector works, review challenges
we faced during production and construction, and report on the
measured performance of the installed detector.

Next I will discuss a prototype Time Projection Chamber (TPC) where
the drift charge is read out with Gas Electron Multipliers (GEMs) and
collected with Pixels. Measurements with cosmic rays suggest that
this technology meets the performance required of the main tracking
detector at a future Linear Collider.

The prototype TPC with GEM + Pixel is just one example of how pixel
technology can be used in new ways. I will close by speculating on
how gas + pixel tracking may be used in another exciting context.

Tuesday March 17th, 10:30am
Nepomuk Otte (SCIPP-UCSC)
"Photon Detector Developments for Future Instruments in Ground Based
Gamma-Ray Astrophysics"

For the last five years, gamma-ray astronomy from the ground provides
us with fantastic results, which address questions in astroparticle
physics, cosmology, and fundamental physics.  The workhorses in the
field are imaging air shower Cherenkov telescopes, which are the most
sensitive instruments to explore the gamma-ray sky above 100 GeV and
are used by H.E.S.S., MAGIC and VERITAS.

For the future large arrays of Cherenkov telescopes are planned,
which will achieve ten times better sensitivity than existing
instruments. In the US the AGIS collaboration pursues an array of  36
Cherenkov telescopes with a Schwarzschild Couder (SC) design.
Among other advantages such as an 8 degree  field of view, the SC  has
a small plate scale, which makes it attractive for small (5x5 mm 2 )
photon detectors. In this context I discuss my work on a novel type of
photon detector, the  Geiger mode APD (G-APD), which is a promising
photon detector not only for AGIS but also of interest for experiments
in high energy physics, medical imaging and industrial applications.

Tuesday March 10th, 10:30am
Vitaliy Fadeyev (SCIPP-UCSC)
"Advanced Detector R&D for ATLAS Upgrade and In Vivo Project in Neurobiology"

I will describe two areas of current research. One area is detector R&D efforts that enable future upgrade of ATLAS experiment. The upgrade poses unique scheduling and technical challenges. I will outline the known driving factors and present two of our projects: planar pixel sensors development and fast data transmission on flexible cables. Under-evaluated but possibly important issues for the upgrade and ways to address them will also be shown.

The second area is in vivo studies in neurobiology. Leveraged against prior developments for retinal research, a multi-channel system is built to investigate information processing in the brain. Its unique features, status of pilot experiments, and future possibilities will be presented.

PLEASE NOTE SPECIAL TIME: Tuesday March 10th, 12:30-1:30pm
Location: ISB 310
Karsten Jedamzik (CC) LPTA, Montpellier
"The Cosmic Lithium Problem(s) and Physics beyond the Standard Model"
Abstract: TBA
Tuesday February 10th, 10:30am
Location: ISB 310
Stefano Profumo (SCIPP)
"Dissecting Pamela (and ATIC) with Occam's Razor: existing, well-known Pulsars naturally account for the "anomalous" Cosmic-Ray Electron and Positron Data"
We argue that both the positron fraction measured by PAMELA and the peculiar spetral features reported in the total differential electron-positron flux measured by ATIC have a very natural explanation in electron-positron pairs produced by nearby pulsars. We show that the greatly improved quality of current data allow us to reverse-engineer the problem: given the regions of pulsar parameter space favored by PAMELA and by ATIC, are there known pulsars that naturally explain the data? We address this question by (1) outlining simple theoretical models for estimating the energy output, the diffusion setup and the injection spectral index of electron-positron pairs, and by (2) considering all know pulsars (as given in the ATNF catalogue). It appears unlikely that a single pulsar be responsible for both the PAMELA result and for the ATIC excess, although two sources are enough to naturally explain both of the experimental results. We list several candidate pulsars that can individually or coherently contribute to explain the PAMELA and ATIC data. We point out that Fermi-LAT will play a decisive role in the very near future, by (1) providing us with an exquisite measurement of the electron-positron flux that will make it possible to distinguish between various pulsar scenarios, and by (2) unveiling the existence of as yet undetected gamma-ray pulsars that can significantly contribute to the local electron-positron flux.
Tuesday February 3rd, 10:30am
Location: ISB 310
Scott Ransom ( National Radio Astronomy Observatory (NRAO))
Astrophysics and Basic Physics from Pulsars in Crowded Places
Double Pulsar Video