Physics Brown Bag Instrumentation Talks
Abstracts and uploaded talks are moving to agenda server.
For current Series Calendar see: Indico agenda server
February 27, 2013: Edwin Westbrook (LANL & LBNL), Al Thompson (LBNL)
"Large Format CMOS-based Detectors for X-ray Diffraction"
See agenda server: https://indico.physics.lbl.gov/indico/conferenceDisplay.py?confId=57
December 5, 2012: Devis Contarato, LBNL
50B-4205, 12:00 noon: "CMOS Active Pixel Sensors as Fast, High Resolution Direct Detectors for Electron Microscopy"
Abstract: CMOS monolithic active pixel sensors have emerged over the past decade as a very attractive option for the design and fabrication of highly integrated radiation detectors that combine the sensitive volume and the readout electronics on the same silicon device, thus enabling the realization of high speed detectors with small pixels, low material budget and robust radiation hardness. Next to developments targeting charged particle tracking at High Energy Physics and Nuclear Science experiments, an effort pioneered by LBNL and originally driven by the TEAM project at the National Center for Electron Microscopy, has resulted in the development of a new generation of high frame rate, high resolution, radiation-hard electron detectors which are revolutionizing digital imaging in Transmission Electron Microscopy. In particular, the direct detection of the incident electrons yields a superior imaging performance with respect to conventional solutions based on optically-coupled CCDs, which are intrinsically limited in point spread function, quantum efficiency and readout speed. The seminar will recount the R&D trajectory of these developments, from the first proof of principle obtained on small scale prototypes to the fabrication of large area, multi-megapixel sensors manufactured in deep-submicron CMOS processes, featuring pixels of micrometer-level pitch and read out at several hundred frames per second. Particular emphasis will be given to our second generation devices, whose technology has been successfully transferred to a commercial partner and is now implemented in a commercial camera system. The first results obtained from the characterization of our latest pixel prototype manufactured in a commercial 65 nm CMOS technology will also be introduced.
October 3, 2012: Adrian Lee, Toki Suzuki, Kaori Hattori UCB/LBNL
50-5132, 2:30 pm:CMB Detector R&D
Abstract: Presentation and brain storming session about integration issues of scaling the fabrication of antenna arrays for CMB to larger sizes.
August 29, 2012: Leo Greiner, LBNL
50-5026 (INPA), 12:00 noon: "A MAPS Vertex Detector for the STAR Experiment at RHIC"
Abstract: The STAR experiment at RHIC is in the process of upgrading the inner detector region of the experiment to improve the vertex resolution. I will
describe the current design of a MAPS based vertex detector which is the innermost and highest resolution detector of the set of three planned upgrade detectors. This detector will enable the identification of decay vertices displaced from the interaction vertex by 100-150 μm and extend the capabilities of the STAR detector in the heavy flavor domain. I will present selected detector design characteristics, prototyping results and the status of the construction.
August 23, 2012: Matthew Szydagis, UC Davis
50-5026 (INPA), 12:00 noon: "NEST, A Model of Scintillation and Electroluminescence in Noble Elements"
A comprehensive model for explaining both the scintillation and electroluminescence absolute yields, and pulse shapes as well, in both liquid and gaseous noble elements will be presented which serves as the foundation for an exhaustive simulation code called NEST (Noble Element Simulation Technique). All available liquid xenon data on both electron and nuclear recoils have been incorporated, and significant progress has been made on extending NEST's applicability to gas xenon and to argon. Results will be shown from Geant4 implementations for 1- and 2-phase xenon detectors. The quasi-empirical NEST approach can lead to a better understanding of detector calibrations and performance verification and aid in the design and optimization of
future detectors for dark matter or double-beta decay, and assist in the data analysis stage of present detectors.
August 9, 2012: Ted Liu, Fermilab
50B-4205, 12:00 noon: "Tracking Trigger R&D for High Luminosity LHC"
It has become clear that track based trigger capability will be crucial to the frontier LHC physics reach in the future, as the luminosity increases. The main physics motivation for the use of track triggers at the LHC is to avoid higher thresholds on single lepton triggers which would be necessary (in some case does not even help), both in ATLAS and CMS, to cope with the highest instantaneous luminosities foreseen for the Phase II upgrades. Track triggers can also be important for triggering on b quarks and leptons, both of which are characteristic of many new physics scenarios. However, due to much higher occupancy and event rates at LHC at high luminosity, and the fact the LHC detectors are much more massive with much larger number of channels in their tracking volumes, there is an enormous challenge in implementing track trigger capability at high luminosity (especially above 1 × 1034cm−2s−1), at Level 1, Level 2 as well as at higher level trigger (HLT). The current technology using fiber data transfer, FPGAs, custom chips and modern PCs cannot be scaled in a simple manner to accommodate all the track trigger demands at different trigger levels. Significant improvements, or breakthroughs, will be needed in order to implement powerful track triggers in the high luminosity LHC environment. In this talk, we will discuss the general tracking trigger issues at high luminosity LHC and some recent R&D activities at Fermilab to address them, including a new approach of using the emerging 3D vertical integration technology to significantly advance the state-of-the-art for fast pattern recognition for the high luminosity LHC as well as for applications outside HEP.
May 23, 2012: Lauren Tompkins, Univ. of Chicago
50A-5132, 12:00 noon: "The new Fast Tracker (FTK) hardware track finder for ATLAS"
The spectacular performance of the LHC machine has forced the ATLAS and CMS detectors to contend with an average of 25 proton-proton interactions per beam crossing in early 2012. Projections for 14 TeV running in 2015 and beyond suggest that the detectors should prepare for up to 80 interactions per crossing. In these dense environments, identifying the physics objects of interest, such as isolated leptons, taus and b-jets is of paramount importance for a successful physics program. The ATLAS experiment is developing a hardware based trigger, FTK, which will perform full silicon detector tracking within 100 microseconds of a Level 1 trigger accept at luminosities of 3x10^34 cm^-2 s^-1, significantly improving the track-based isolation, secondary vertex tagging and track-based tau finding at the Level 2 trigger. I will discuss the FTK design and performance prospects, as well as say a few words about FTK-like systems in future upgrades.
April 18, 2012: Lindsay Glesener, UC Berkeley SSL
50B-4205, 12:00 noon:"Silicon strip detectors for the Focusing Optics X-ray Solar Imager"
The Focusing Optics X-ray Solar Imager (FOXSI) is a sounding rocket payload carrying grazing-incidence X-ray optics and silicon strip detectors. In its 2012 maiden flight, FOXSI will observe X-rays from the Sun at energies from 4 to 15 keV and will make the first measurements of nonthermal X-rays from the quiet regions of the Sun. In order to meet the mission's requirements for spatial resolution (<12 arcseconds), energy resolution (<1 keV), and low energy threshold (< 5 keV), doubled-sided silicon strip detectors are utilized. These detectors were developed at ISAS in Sagamihara, Japan as candidates for the Astro-H astrophysics mission. The detectors have 75 um-pitch strips and are read out out by a set of ASICs that perform triggering, sample-and-hold, and AD conversion. A second rocket flight in 2014 will feature improvements to the optics and will use CdTe detectors for improved efficiency at higher energies.
March 21, 2012: Abder Mekkaoui, LBNL
February 15, 2012: Victor Gehman, LBNL
There are a large number of direct dark matter and neutrino detection experiments either in construction or in planning which will use the scintillation light from noble elements as a mechanism for measuring radiation deposition. This scintillation light is emitted in extreme ultraviolet (EUV, 100 - 200 nm) wavelengths. There are very few photon detectors directly sensitive to this wavelength that are also capable of detecting the very small number of photons expected from signal events in such detectors. One of the most technically feasible solutions to this problem is to use a thin film of Tetraphenyl Butadiene (TPB) as a fluor. The TPB film shifts the EUV photons to visible photons, detectable with commercial photomultiplier tubes. Here we present a study of the fluorescence efficiency of such films as well as the shape of the visible re-emission spectral shape at several input EUV wavelengths. We will also discuss plans for future studies, especially as the relate to experiments with a major contribution from LBNL.
November 30, 2011: Erik Brubaker, Sandia National Lab., Livermore, CA
50B-4205, 12:00 noon:"Fast Neutron Detection and Imaging for Nuclear Security Applications"
Fission-energy neutrons are a highly specific signature of special nuclear material. Because of their penetrating nature and low natural backgrounds, fast neutrons can be used to detect and locate significant quantities of plutonium with passive instruments, or highly enriched uranium if active interrogation is employed. Typical applications require large-area (~m^2) systems in order to capture appreciable neutron flux, and large volumes of liquid scintillator or other active material due to low interaction cross-sections. Adding directional capabilities to neutron detectors both improves detection thresholds by enhancing signal/background discrimination and allows imaging of the source distribution; however, different applications require instruments optimized in different ways. At Sandia National Laboratories, we have developed, built, and tested fast neutron imagers based on a variety of concepts, in many cases for the first time anywhere. These include the Neutron Scatter Camera, fast neutron coded aperture imagers, time-encoded imaging, pinhole imagers, and more. In this talk, I will describe several of the detectors we have built, and discuss some of the tradeoffs involved in tailoring detector capabilities to particular performance needs.
July 26, 2011: Lior Arazi, Weizmann Institute of Science, Rehovot, Israel
50A-5132, 12:00 noon:"Diffusing Alpha-Emitters Radiation Therapy – A New Concept in Solid Tumor Treatment"
Alpha particle irradiation has been known for decades to be highly lethal to individual cancer cells, with many radiobiological advantages over photons and electrons. However, no practical way has so far been found to utilize alpha particles against macroscopic tumor masses, largely because of their exceedingly short range. We propose a new approach – Diffusing Alpha-Emitters Radiation Therapy (DαRT) – that enables enhancing the therapeutic range of alpha particles from the micrometer to the millimeter domain, thus allowing the treatment of large tumor masses. The basic idea is to add an intermediate layer between the physical source and the alpha emission event – namely, a short-lived alpha emitter which diffuses to considerable distances from the source prior to emitting an alpha particle. In this scheme, the tumor is treated by an array of implanted sources bearing alpha emitting atoms a few nanometers below their surface. As these atoms disintegrate, their daughters, which are short-lived alpha-emitters themselves, recoil into the tumor, spread through its volume and decay at therapeutically significant distances. Each source generates a 'kill zone' spanning several millimeters, as determined by the interplay between diffusive and convective processes inside the tissue on one hand and the effective lifetime of the diffusing atoms on the other. The method was extensively tested on mice tumors with promising results, ranging from substantial reduction in tumor growth to complete tumor regression with no recurrence, and is now being developed towards a first clinical trial. DαRT’s main attraction lies in its ability to deliver therapeutic high LET doses to the tumor with potentially negligible damage to adjacent healthy tissue, thus making it a promising tool for treating unresectable tumors which cannot be irradiated by conventional methods.
June 21, 2011: L. Caminada, D. Contarato, S. Diez-Cornell, M. Gilchriese, C. Grace, and J-P. Walder, LBNL
50B-4205, 12:15pm:"Highlights from TIPP conference"
Review of most interesting slides from the various sessions. Slides were presented in this order: S. Diez-Cornell, C. Grace (or powerpoint with movies),L. Caminada, D. Contarato, M. Gilchreise, J-P. Walder (click each name for slides in pdf)
May 25, 2011: Azriel Goldschmidt, LBNL
At LBNL we have designed and built a 1kg prototype TPC towards a 100 kg enriched 136Xe detector for the search of neutrinoless double beta decay at the Canfranc as part of the NEXT collaboration. Using electroluminescence as a gain mechanism an excellent energy resolution may be obtained, only a factor 2-3 from Germanium detectors, along with electron tracking information useful for background rejection. I will show initial results from our TPC prototype and will discuss the path and challenges towards a full scale experiment. Other possible applications of this technology will be discussed as well.
May 5, 2011: Gianluigi De Geronimo, Brookhaven National Lab.
50B-4205, 10:00am: "Front-end ASICs for high resolution detectors"
Application Specific Integrated Circuits (ASICs) have enabled entirely new classes of radiation detectors to be constructed. ASICs combine high channel density, high functionality, low noise and low power, and can offer high yield, high reliability and long lifetime. After an introduction to the state-of-the-art and to the typical design-flow, some of our most recent front-end ASIC developments will be presented. Details on the peak detection circuit for amplitude and timing measurements will be given. An ASIC for operation in cryogenic environment will be introduced, with highlights on CMOS performance and input MOSFET optimization. Finally, the prospects for Germanium sensors will be discussed.
March 23, 2011: Maurice Garcia-Sciveres, LBNL
50A-5132, 12:15pm: "The FE-I4 pixel detector readout chip"
A new pixel readout integrated circuit called FE-I4A has been fabricated in 130nm feature size CMOS technology. It represents the new state of the art in hybrid pixel readout for particle tracking, containing many innovations to increase rate capability, reduce power, reduce cost, and increase position resolution, cmpared to the generation of pixel detectors operating today at the LHC. The design was an international collaborative effort led by LBNL, resulting in an 80 million transistor device that works virtually error free on the first full size run. The nature of such remote technical collaboration will be explained, and the design approaches that (we like to think) led to the very successful run will be presented. The first detector to make use of FE-I4 will be the Insertable B-Layer upgrade to ATLAS (IBL), now planned for 2013. For this reason a revision called FE-I4B is now under preparation with intent to submit it for fabrication as the IBL production chip this summer.
February 23, 2011: Ke Han, LBNL
50B-4205, 12:00pm: "Large mass bolometers for rare event searches"
A bolometer measures the energy deposition through a corresponding temperature rise. The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton scale bolometric experiment to search for neutrino-less double beta decay in 130Te. In CUORE, a single bolometer module consists mainly of a 5x5x5 cm3 tellurium oxide crystal, a silicon heater, and one or two neutron transmutation doped germanium thermistors. Running at 10 mK base temperature, the bolometer module can achieve an energy resolution of 5 keV (0.2%) at the energy region of interest of neutrinoless DBD. With 988 such modules, an expected background of 0.01 counts per (keV kg year), and five years of running time, CUORE will be one of the most competitive DBD experiments on the horizon. Meanwhile at Berkeley, we start the next generation bolometer R&D work with a newly installed dilution refrigerator. Our effort will focus on new bolometric materials and scintillation or ionization readout besides phonons for better particle identification.
November 10, 2010: Sherwood Parker, U. of Hawaii
50A-5132, 12:00pm: "Fast Signals and New Challenges in Silicon Detectors "
The talk will follow silicon detector signals, especially fast ones (possibly sub-nanosecond), from their creation by ionizing particles, through their entrance into an amplifier via Ramo’s theorem (with feedback playing a vital role) to what happens once they leave the amplifier.
This will involve a silicon 3D sensor with extreme radiation hardness and high-speed potential, both coming from the same feature, and both vital for several new applications. The very fastest type has only been made in small trial versions so we will show fast signals from its predecessor. The final topic will involve a new task for silicon detectors.
April 28, 2010: Hanh-Phuc Le , UC Berkeley
50A-5132, 12:00pm: "Fully-Integrated Power Management with Switched-Capacitor DC-DC Converters"
With the rising integration levels used to increase digital processing performance, there is a clear need for multiple independent on-chip supplies in order to support per-block power management. Simply adding multiple off-chip DC-DC converters is not only difficult due to supply impedance concerns, but adds cost to the platform by increasing motherboard size and package complexity. There is therefore a strong motivation to integrate voltage conversion on the silicon.
In this presentation I will discuss the motivations of using switched-capacitor (SC) DC-DC converters versus the counter-part inductor-based converters in general and, in particular, for fully-integrated implementations. Analysis and design for SC converters will also be included in detail with implemented prototypes.
December 9, 2009: Craig Tindall, LBNL
50B-4205 12:00pm: "Silicon Detectors for Space Instrumentation"
The Semiconductor Detector Group at LBNL has been involved in two collaborative projects to develop silicon detectors for space instrumentation. The first, with NASA and the UCB Space Sciences Laboratory involved fabricating detectors with a very thin entrance contact in order to reduce the detection threshold for low energy particles. Until now, windowless electron multipliers combined with electrostatic or magnetic analyzers have generally been used to measure particle distributions with energies below about 20 keV. Because of their sensitivity to low energy particles, thin window silicon detectors do not require electrostatic or magnetic analyzers and thus significantly reduce the instrument size, weight and power requirements. Furthermore, the low intrinsic background counting rate of semiconductor detectors enables one to measure phenomena not accessible to analyzer/electron multiplier based instruments such as weak impulsive electron events. Detectors of this type have flown on the Solar Terrestrial Relations (STEREO) spacecraft, and the Time History of Events and Macroscale Interactions During Substorms (THEMIS) mission. Fabrication methods and performance of these detectors will be reviewed.
An ongoing second project, with NASA, the Jet Propulsion Laboratory (JPL) and the California Institute of Technology (CIT), has as its goal the production of ultra-thin silicon detectors for use in space instruments utilizing the dE/dx vs. total energy particle identification technique. To be useful in identifying particles with energies of about 1 MeV/nucleon, the detector must be < 10 um thick. To date we have successfully fabricated detectors that are 15 um thick using silicon on insulator (SOI) starting material. These detectors exhibit very low leakage currents and have been successfully tested using Am-241 alpha particles. The fabrication technique used and test results will be presented.
September 9, 2009:
Vitaliy Fadeyev, UC Santa Cruz
50B-4205 12:00pm: "Making Multi-channel Readout Systems for Neurobiology"
System neuroscience is a vast field of science with the goal to understand the inner workings of one of the most complex creations of nature, the brain. For most of its history, the progress has been made with fairly simple means. I will describe technical aspects of making multi-channel recording systems with the goal of extracting more information about the neural circuits than was previously available. Such systems can monitor, and in some cases, stimulate activity of an ensemble of neurons in live animals. This development builds upon prior successful retina studies. The status of several experimentation programs will be presented.
May 11, 2009:
Marc Christophersen, US Naval Research Lab
50A-5132 12:00pm: "Micro-machined silicon detectors"
This talk will present two novel detectors which are enabled by modern micro-machining techniques. The potential of micro-machined silicon as a radiation detector was first introduced by S. Parker et al. as radiation-hard detectors, often called 3-D detectors. We present a curved radiation detector. As vertex detectors for smaller inner beam pipe diameters are required; the planar nature of the detector becomes more and more of a problem. Both strip detectors and
pixel arrays have been realized on a curved topography. We demonstrated low-noise performance by successfully detecting low-energy gamma-ray with a curved strip detector. Beside the curved detector, we present 3-D detectors for use as thick gamma-ray detectors. Current room-temperature gamma-ray detectors are built in planar device architecture. We use micro-machining techniques to introduce vertical electrodes, which allow lateral charge collection, decoupling thickness and charge collection properties. The ultimate goal is the ability to form cm thick gamma-ray detectors. The vertical electrodes are micro-machined trenches with depth up to 1.7 mm in silicon. We present the basic detector structure, finite element simulations, and radiation measurements.
April 16, 2009:
Matteo Staffaroni, UC Berkeley
50B-4205 12:00pm: "The Trouble with Magnetic Storage: Why Your Next Hard Drive Will Come with a Few Lasers On the Side"
The areal density of magnetic storage media has been growing exponentially, paralleling Moore's Law, since IBM first introduced the commercial hard disk drive in 1956. While the semiconductor industry is not expected to run into trouble keeping up with Moore's law before 2030, when most device parameters will simulataneously reach fundamental
physical limits, the magnetic storage industry is already in trouble as the magnetic domains used to store information on hard disks are becoming so small that they can no longer maintain their magnetization in the face of random thermal energy fluctuations. To maintain the historical areal density growth rate, sometime around 2012 the magnetic industry is expected to begin using a new recording technique known as heat assisted magnetic recording (HAMR). This technique relies on the availability of near field transducers that efficiently focus energy to the nanoscale. As the problem has been known for some time, several ideas have been put forth for such transducers, however none has come out ahead as a clearly superior device. Here we survey the current art and review the underlying physics using Maxwell's equations.
We then introduce a lumped element approach to plasmonics, which we use to arrive at an optimal design for an efficient near field transducer able to achieve a level of energy focusing that meets the projected requirements for the the first generation of heat assisted magnetic recording.
March 25, 2009:
Azriel Goldschmidt, LBNL
50B-4205 12:00pm: "High Pressure Gaseous Xenon Imager with Optimum Energy Resolution for
Neutrinoless Double Beta Decay"
High pressure gaseous (room temperature) xenon detectors can offer excellent energy resolution (just a factor of three worse than Germanium diodes) along with imaging capabilities for electrons in the ~MeV energy region. Unlike conventional avalanching, electro-luminescence can be used to provide inherent gain without degrading the intrinsic resolution. A Time Projection Chamber that images electron tracks and measures their energy will be described along with its expected performance.
These detectors should scale well to the ~1 ton scale likely required to observe the rare neutrinoless double beta decay of Xe136 and provide powerful background rejection tools against the ubiquitous gamma rays from natural radiation from materials in and around the detector. Other possible uses of this new technique will be also presented.
February 3, 2009:
Henry J. Frisch, Univ. of Chicago,
50A-5132 12:00pm: "First Steps Toward Developing Large-Area Fast Photo-detectors"
A group of us have been working in the style of a pick-up ballgame to develop very large-area fast planar photo-detectors. The proposed detectors would have integrated transmission-line readout and sampling electronics able to achieve timing and position resolutions in the range of 1-50 psec and 1-10 mm, respectively, depending on the application. The capability for very precise time measurements is inherent in the design, and provides a `third' coordinate, orthogonal to the two in the plane, for the point of origin of photons or charged particles, allowing `tomographic' reconstruction in 3-dimensions inside a volume. The proposed designs are modular and hence are economically scalable to very large areas, suitable for collider detectors, very large water Cherenkov counters, medical imaging, and scanners for transportation security. The three main thrusts of the effort are in psec-resolution front-end electronics, micro-channel plate understanding and designs, and simulation. We have made a good start in all three areas, and the many problems we are learning about are interesting. Not yet seeing any show-stoppers, we are, perhaps foolishly, getting more ambitious.
October 30, 2008:
Harry van der Graaf, NIKHEF, The Netherlands.
50A-5132 12:00pm: "Towards new gaseous tracking detectors"
100 years ago Hans Geiger operated the first gaseous detector, which was the basis for 'wire chambers', widely applied as track imaging in particle physics experiments. In wire chambers gas amplification occurs, close to the wire surface, due to the strong (1/R) electric field. This enables the detection of the few single electrons created in the gas by ionisation radiation.
In Micro Pattern Gas Detectors, areas with a strong electric avalanche field are created by two or more conductive perforated planes (grid). The granularity of such a detector is determined by the hole pitch and can be much better in comparison to wire chambers.
In another development, each grid hole is equipped with its own readout channel (preamp, shaper, discriminator) in the form of an active pixel array in a CMOS chip. The combination of an (integrated) grid and the pixel readout enables high spatial resolution, good time resolution (thus precise 3rd (drift) coordinate), fast signal development, low occupancy and low ion feedback. By means of MEMS technology we integrated the Micromegas grid onto pixel chips (InGrid), forming a monolithic readout unit for gaseous detectors.
Essentially, the application of gas as detection material, compared to, for instance, Si, offers several advantages, relevant for future tracking and imaging detector developments.
If newly-to-develop electron emission foils could be made with sufficient efficiency to emit an electron after the passage of a minimum ionizing particle, the gaseous drift layer could be omitted, and the foil, without holes, could replace InGrid. Micro Channel Plates, possibly integrated onto the CMOS pixel chip, would eliminate the gas entirely. This would result in an ultra fast monolithic solid state foil detector for, for instance, CLIC experiments
Harry van der Graaf (firstname.lastname@example.org (mailto:\(email@example.com)) obtained his PhD in 1986, at Delft University of Technology, on Signal Development and -Processing in MWPCs. Working for Nikhef, he was involved in the muon chambers of the L3 experiment at CERN, and, after that, the drift chambers for the ATLAS Muon Spectrometer. He developed the RASNIK alignment system which is used also outside particle physics experiments. Since 2001 he is working on a new generation of gaseous detectors, to be applied in future detectors at ILC, CLIC and SuperLHC.
October 2, 2008:
Toshinori Abe, University of Tokyo (Aihara group)
50A-5132 12:00pm....:"R&D status of large aperture Hybrid Avalanche Photo-detector (HAPD)"
We report on the R&D status of large aperture Hybrid Avalanche Photo-detector (HAPD). The 13in HAPD is being developed to replace photo-electron multiplier tube (PMT) in the next generation water Cherenkov detectors such as Hyper Kamiokande. We discuss the excellent performance of HAPD (~200ps time resolution and clear photo-electron separation of up to 5) compared to PMT and the readout system dedicated for HAPD.
July 30, 2008:
John Vallerga, UCB Space Sciences lab
50A-5132 12:00pm....:"readout of microchannel plate detectors
for high dynamic range photon/particle imaging using Medipix2/Timepix CMOS ASIC"
July 16, 2008:
Allon Hochbaum, UC Berkeley
50A-5132 12:00pm....:"Thermal transport in semiconductor nanowires"
Thermoelectric materials can convert waste heat to electricity, potentially resulting in significant fuel savings and reductions in carbon emissions. Their efficiency depends on the thermoelectric figure of merit (ZT), which is proportional to the Seebeck coefficient and temperature, and inversely proportional to the electrical resistivity and thermal conductivity (k). In the past, it has been challenging to increase ZT > 1 since the parameters of ZT are generally interdependent in bulk. Here we report the wafer-scale electrochemical synthesis and thermoelectric
characterization of rough silicon nanowires with enhanced ZT relative to the bulk material. Single nanowire measurements show that their electrical resistivity and Seebeck coefficient are similar to those of optimally doped bulk Silicon. The thin nanowires, however, exhibit a 100-fold reduction in k, yielding a large ZT = 0.6 at 300K and increasing with temperature. For such nanowires, the lattice k approaches the silicon amorphous limit, which cannot be explained by current phonon transport theories. Although bulk silicon is a poor thermoelectric material, silicon nanowire arrays show promise as high-performance, scalable thermoelectric materials. Moreover, the efficient phonon scattering mechanisms in these nanowires may serve as guides to decouple thermoelectric parameters and enhance ZT in other materials as well.
April 13, 2006:
Seung Ji, Lauren Tompkins, LBNL
50B-6208 12:00pm....:"Student Edition Brown Bag" (Two 20 minute talks)
1) "0.13um CMOS Read Out chip test progress report" by Seung K. Ji
A 0.13um CMOS front end chip is one of options for a future upgrade of ATLAS pixel detector. For studying 0.13um CMOS technology, the Berkeley group developed a prototype 0.13um Read Out chip 2 years ago. In this seminar, I will talk about the charateristics of the test Read Out chip ,my test setup, and preliminay results of the first two irradiation tests.
2) "Monolithic Pixel Senor Development and Testing at LBNL" by Lauren Tompkins
We present silicon pixel sensor development results from the International Linear Collider group at LBNL. First we will discus results from the first sensor to be designed at LBL for the ILC group, and then we will review our work on backthinning existing sensors. Basic principles of CMOS sensors and the ILC requirements for pixel
detectors will also be addressed.
March 23, 2006:
Maximilian Fabricius, Evan Wulf, LBNL
50B-6208 12:00pm....:'''Student Edition Brown Bag''' (Three 15-20 minute talks)
1)"ATLAS Stave construction and testing" by Evan Wulf:
Description of prototype silicon strip macro-assembly called "stave" aimed at inner detector upgrade for SuperLHC. Assembly steps and electrical tests performed at LBNL.
2)"Quantum efficiency characterization of LBNL's back-illuminated CCDs" by Maximilian Fabricius:
It will be explained briefly what a CCD is, why LBNL develops these special CCDs for SNAP and what the difference between "normal" astronomical CCDs and the LBNL CCCs is. I will explain how we measure the quantum efficiency and why this measurement is difficult. Finally I will show how a reflectivity measurement can verify the QE estimates and show the reflectometer we built for this reason.
March 17, 2006:
Piero Giubilato, INFN and University of Padova, Italy
50B-4205 12:00pm....:"Novel techniques for radiation hardness characterisation"
The speaker will be discussing a [http://sirad.pd.infn.it/people/piero/phd/Piero_PhD_Thesis_1a.pdf thesis] on radiation hardness of CMOS Si devices based on
work performed at Legnaro and Sandia. The main topic is SEU testing.
February 9, 2006:
Ken Shepard, Columbia University
50B-4205 12:00pm....:"Circuit techniques for on-chip power management"
Power distribution is becoming a challenging issue in advanced CMOS processes as supply voltages scale lower and current levels increase. High current levels exacerbate power supply network impedance requirements, forcing large amounts of decoupling capacitance and stringent limits on resistance and inductances in power distribution
networks. This problem can be effectively addressed if power can instead by delivered at high voltages, reducing current levels, and then down-converted on chip. Switching regulators, while energy efficient, defy on-chip integration because of the need for large, high-Q on-chip inductors. We will describe an early on-chip power management system based on linear regulators and switched capacitor supplies that demonstrated the practical
infeasibility of high energy efficiencies with these approaches. Our most recent efforts involve stacking circuits to operate from a voltage supply that is a multiple of the nominal supply voltage. Dc-dc downconversion is performed through charge recycling without the need for explicit downconverters. Experiments results demonstrate efficiencies
for 2Vdd-to-Vdd downconversion in excess of 93%.
For the STAR Detector at RHIC