H.F.-W. Sadrozinski

University of California, Santa Cruz, Santa Cruz, California, United States

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Publications (643)1284.42 Total impact

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    ABSTRACT: Transient current technique (TCT) measurements with focused laser light on miniature silicon strip detectors (n+-type strips on p-type bulk) with one inactive edge thinned to about 100 µm using the Scribe-Cleave-Passivate (SCP) method are presented. Pulses of focused IR (λ=1064 nm) laser light were directed to the surface of the detector and charge collection properties near the slim edge were investigated. Measurements before and after irradiation with reactor neutrons up to 1 MeV equivalent fluence of 1.5×1015 neq/cm2 showed that SCP thinning of detector edge does not influence its charge collection properties. TCT measurements were done also with focused red laser beam (λ=640 nm) directed to the SCP processed side of the detector. The absorption length of red light in silicon is about 3 µm so with this measurement information about the electric field at the edge can be obtained. Observations of laser induced signals indicate that the electric field distribution along the depth of the detector at the detector edge is different than in the detector bulk: electric field is higher near the strip side and lower at the back side. This is a consequence of negative surface charge caused by passivation of the cleaved edge with Al2O3. The difference between bulk and edge electric field distributions gets smaller after irradiation.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 07/2014; 751:41–47. · 1.32 Impact Factor
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    ABSTRACT: AC-coupled silicon strip sensors can be damaged in case of a beam loss due to the possibility of a large charge accumulation in the bulk, developing very high voltages across the coupling capacitors which can destroy them. Punch-through structures are currently used to avoid this problem helping to evacuate the accumulated charge as large voltages are developing. Nevertheless, previous experiments, performed with laser pulses, have shown that these structures can become ineffective in relatively long strips. The large value of the implant resistance can effectively isolate the “far” end of the strip from the punch-through structure leading to large voltages. We present here our developments to fabricate low-resistance strip sensors to avoid this problem. The deposition of a conducting material in contact with the implants drastically reduces the strip resistance, assuring the effectiveness of the punch-through structures. First devices have been fabricated with this new technology. Initial results with laser tests show the expected reduction in peak voltages on the low resistivity implants. Other aspects of the sensor performance, including the signal formation, are not affected by the new technology.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 06/2014; · 1.32 Impact Factor
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    ABSTRACT: Proton radiography has applications in patient alignment and verification procedures for proton beam radiation therapy. In this paper, we report an experiment which used 200 MeV protons to generate proton energy-loss and scattering radiographs of a hand phantom. The experiment used the first-generation proton computed tomography (CT) scanner prototype, which was installed on the research beam line of the clinical proton synchrotron at Loma Linda University Medical Center. It was found that while both radiographs displayed anatomical details of the hand phantom, the energy-loss radiograph had a noticeably higher resolution. Nonetheless, scattering radiography may yield more contrast between soft and bone tissue than energy-loss radiography, however, this requires further study. This study contributes to the optimization of the performance of the next-generation of clinical proton CT scanners. Furthermore, it demonstrates the potential of proton imaging (proton radiography and CT), which is now within reach of becoming available as a new, potentially low-dose medical imaging modality.
    IEEE Transactions on Medical Imaging 04/2014; 33(4):875-881. · 3.80 Impact Factor
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    ABSTRACT: These reports present the results of the 2013 Community Summer Study of the APS Division of Particles and Fields ("Snowmass 2013") on the future program of particle physics in the U.S. Chapter 8, on the Instrumentation Frontier, discusses the instrumentation needs of future experiments in the Energy, Intensity, and Cosmic Frontiers, promising new technologies for particle physics research, and issues of gathering resources for long-term research in this area.
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    ABSTRACT: This paper reports on the first characterization of double sided 3D silicon radiation pixel detectors with slim edges. These detectors consist of a three-dimensional array of electrodes that penetrate into the detector bulk with the anode and cathode electrodes etched from opposite sides of the substrate. Different detectors were post-processed using the scribe-cleave-passivate (SCP) technology to make "slim edge" sensors. These sensors have only a minimal amount of inactive peripheral region, for the benefit of the construction of large-area tracker and imaging systems.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 12/2013; · 1.32 Impact Factor
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    ABSTRACT: We are pursuing scribe-cleave-passivate (SCP) technology of making "slim edge" sensors. Such sensors have only a minimal amount of inactive peripheral region, which benefits construction of large-area tracker and imaging systems. Key application steps of this method are surface scribing, cleaving, and passivation of the resulting sidewall. We are working on developing both the technology and physical understanding of the processed devices performance. In this paper we begin by reviewing the manufacturing options of SCP technology. Then we show new results regarding the technology automation and device physics performance. The latter includes charge collection efficiency near the edge and radiation hardness study. We also report on the status of devices processed at the request of the RD50 collaborators.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 12/2013; · 1.32 Impact Factor
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    ABSTRACT: A search is made for massive long-lived highly ionising particles with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb-1 of pp collision data taken at sqrt(s)=7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e <= |q| <= 17e and masses 200 GeV <= m <= 1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism.
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    ABSTRACT: We propose to develop a fast, thin silicon sensor with gain capable to concurrently measure with high precision the space (˜10 μm) and time (˜10 ps) coordinates of a particle. This will open up new application of silicon detector systems in many fields. Our analysis of detector properties indicates that it is possible to improve the timing characteristics of silicon-based tracking sensors, which already have sufficient position resolution, to achieve four-dimensional high-precision measurements. The basic sensor characteristics and the expected performance are listed, the wide field of applications are mentioned and the required R&D topics are discussed.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 12/2013; · 1.32 Impact Factor
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    ABSTRACT: Sensors play a key role in detecting both charged particles and photons for all three frontiers in Particle Physics. The signals from an individual sensor that can be used include ionization deposited, phonons created, or light emitted from excitations of the material. The individual sensors are then typically arrayed for detection of individual particles or groups of particles. Mounting of new, ever higher performance experiments, often depend on advances in sensors in a range of performance characteristics. These performance metrics can include position resolution for passing particles, time resolution on particles impacting the sensor, and overall rate capabilities. In addition the feasible detector area and cost frequently provides a limit to what can be built and therefore is often another area where improvements are important. Finally, radiation tolerance is becoming a requirement in a broad array of devices. We present a status report on a broad category of sensors, including challenges for the future and work in progress to solve those challenges
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    ABSTRACT: A unique CMOS chip has been designed to serve as the front-end of the tracking detector data acquisition system of a pre-clinical prototype scanner for proton computed tomography (pCT). The scanner is to be capable of measuring one to two million proton tracks per second, so the chip must be able to digitize the data and send it out rapidly while keeping the front-end amplifiers active at all times. One chip handles 64 consecutive channels, including logic for control, calibration, triggering, buffering, and zero suppression. It outputs a formatted cluster list for each trigger, and a set of field programmable gate arrays merges those lists from many chips to build the events to be sent to the data acquisition computer. The chip design has been fabricated, and subsequent tests have demonstrated that it meets all of its performance requirements, including excellent low-noise performance.
    IEEE Transactions on Nuclear Science 10/2013; 60(5):3262-3269. · 1.46 Impact Factor
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    Physics Letters B. 04/2013; 721(s 1–3):32–50.
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    ABSTRACT: This paper discusses the design and operation of the 1st proton CT scanner for 3D imaging. Reduction of proton range uncertainties and improved dose accuracy in the patient for treatment planning are central goals. A central CT slice acquired by reconstruction of 134 million proton tracks through a 14 cm spherical polystyrene phantom with high and low density inserts is presented.
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    ABSTRACT: All silicon wafers are singulated into individual chips after device processing (front-end) and before packaging. Silicon wafer singulation is dominated by blade- and laser-dicing techniques, both leave some damage. We are using scribing and cleaving to singulate silicon radiation detectors. Scribing and cleaving is known to leave almost damage free sidewalls when applied to III–V compound semiconductors. The technique is not well developed for dicing silicon devices. We used silicon sensors working in a full depletion mode to determine the damage from different scribing techniques (laser-, diamond, and etch-scribing). Etch-scribing shows very low leakage currents and enables cuts at the edge of the active area of the sensor/die. Furthermore, the leakage currents for laser- and diamond-scribed devices can be reduced by a gaseous sidewall etch step.
    Solid-State Electronics 03/2013; 81:8–12. · 1.51 Impact Factor
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    ABSTRACT: Pixel detectors with cylindrical electrodes that penetrate the silicon substrate (so called 3D detectors) offer advantages over standard planar sensors in terms of radiation hardness, since the electrode distance is decoupled from the bulk thickness. In recent years significant progress has been made in the development of 3D sensors, which culminated in the sensor production for the ATLAS Insertable B-Layer (IBL) upgrade carried out at CNM (Barcelona, Spain) and FBK (Trento, Italy). Based on this success, the ATLAS Forward Physics (AFP) experiment has selected the 3D pixel sensor technology for the tracking detector. The AFP project presents a new challenge due to the need for a reduced dead area with respect to IBL, and the in-homogeneous nature of the radiation dose distribution in the sensor. Electrical characterization of the first AFP prototypes and beam test studies of 3D pixel devices irradiated non-uniformly are presented in this paper.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 02/2013; · 1.32 Impact Factor
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    ABSTRACT: Reduced edge or ``edgeless'' detector design offers seamless tileability of sensors for a wide range of applications from particle physics to synchrotron and free election laser (FEL) facilities and medical imaging. Combined with through-silicon-via (TSV) technology, this would allow reduced material trackers for particle physics and an increase in the active area for synchrotron and FEL pixel detector systems. In order to quantify the performance of different edgeless fabrication methods, 2 edgeless detectors were characterized at the Diamond Light Source using an 11 μm FWHM 15 keV micro-focused X-ray beam. The devices under test were: a 150 μm thick silicon active edge pixel sensor fabricated at VTT and bump-bonded to a Medipix2 ROIC; and a 300 μm thick silicon strip sensor fabricated at CIS with edge reduction performed by SCIPP and the NRL and wire bonded to an ALiBaVa readout system. Sub-pixel resolution of the 55 μm active edge pixels was achieved. Further scans showed no drop in charge collection recorded between the centre and edge pixels, with a maximum deviation of 5% in charge collection between scanned edge pixels. Scans across the cleaved and standard guard ring edges of the strip detector also show no reduction in charge collection. These results indicate techniques such as the scribe, cleave and passivate (SCP) and active edge processes offer real potential for reduced edge, tiled sensors for imaging detection applications.
    Journal of Instrumentation 01/2013; 8:P01018. · 1.53 Impact Factor
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    ABSTRACT: The effectiveness of punch-through protection (PTP) structures on n-on-p AC-coupled silicon strip detectors using pulses from a 1064 nm IR laser, which mimics beam accidents, is investigated. The voltages on the strip implants are measured as a function of the bias voltage and incoming particle flux. We present a 4-resistor model to describe the sensor after large particle fluxes, which is then used to characterize the effectiveness of PTP structures. The effectiveness of PTP structures is presented in terms of total strip implant to bias rail length, type of surface treatment used for strip isolation, coverage of the polysilicon bias resistor, and radiation damage from protons, neutrons and pions.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2013; 699:31–35. · 1.32 Impact Factor
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    ABSTRACT: Silicon detectors normally have an inactive region along the perimeter of the sensor. In this paper we describe a “scribe, cleave, and passivate” (SCP) technique for the fabrication of slim edges in a post processing with finished detectors. The scribing was done by laser-scribing and etching. After scribing and cleaving steps, the sidewalls are passivated with a dielectric. We present results for n- and p-type sensors with different sidewall passivations. The leakage current depends strongly on the type of sidewall passivation. An alumina passivation leads to very low leakage currents for p-type sensors because of a negative interface charge. For n-type sensors, a hydrogenated silicon nitride shows the lowest leakage currents. Furthermore, we applied the technique to large area n-type single-sided strip detectors (cleaving length up to 3.5 cm).
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2013; 699:14–17. · 1.32 Impact Factor
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    ABSTRACT: The Fermi Large Area Telescope (Fermi-LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy γ-ray telescope, covering the energy range from 20 MeV to more than 300 GeV. During the first years of the mission, the LAT team has gained considerable insight into the in-flight performance of the instrument. Accordingly, we have updated the analysis used to reduce LAT data for public release as well as the instrument response functions (IRFs), the description of the instrument performance provided for data analysis. In this paper, we describe the effects that motivated these updates. Furthermore, we discuss how we originally derived IRFs from Monte Carlo simulations and later corrected those IRFs for discrepancies observed between flight and simulated data. We also give details of the validations performed using flight data and quantify the residual uncertainties in the IRFs. Finally, we describe techniques the LAT team has developed to propagate those uncertainties into estimates of the systematic errors on common measurements such as fluxes and spectra of astrophysical sources.
    The Astrophysical Journal Supplement Series 10/2012; 203(1):4. · 14.14 Impact Factor
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    ABSTRACT: We report on the detection of high-energy γ-ray emission from the Moon during the first 24 months of observations by the Fermi Large Area Telescope (LAT). This emission comes from particle cascades produced by cosmic-ray (CR) nuclei and electrons interacting with the lunar surface. The differential spectrum of the Moon is soft and can be described as a log-parabolic function with an effective cutoff at 2-3 GeV, while the average integral flux measured with the LAT from the beginning of observations in 2008 August to the end of 2010 August is F (> ##IMG## [http://ej.iop.org/images/0004-637X/758/2/140/apj445159ieqn1.gif] $100 rm MeV) =(1.04pm 0.01,rm [statistical error]pm 0.1,rm [systematic error])times 10^-6$ cm –2 s –1 . This flux is about a factor 2-3 higher than that observed between 1991 and 1994 by the EGRET experiment on board the Compton Gamma Ray Observatory , F (>100 MeV) ##IMG## [http://ej.iop.org/icons/Entities/ap.gif] ≈ 5 × 10 –7 cm –2 s –1 , when solar activity was relatively high. The higher γ-ray flux measured by Fermi is consistent with the deep solar minimum conditions during the first 24 months of the mission, which reduced effects of heliospheric modulation, and thus increased the heliospheric flux of Galactic CRs. A detailed comparison of the light curve with McMurdo Neutron Monitor rates suggests a correlation of the trends. The Moon and the Sun are so far the only known bright emitters of γ-rays with fast celestial motion. Their paths across the sky are projected onto the Galactic center and high Galactic latitudes as well as onto other areas crowded with high-energy γ-ray sources. Analysis of the lunar and solar emission may thus be important for studies of weak and transient sources near the ecliptic.
    The Astrophysical Journal 10/2012; 758(2):140. · 6.28 Impact Factor
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    ABSTRACT: We report an analysis of the interstellar γ-ray emission from the Chamaeleon, R Coronae Australis (R CrA), and Cepheus and Polaris flare regions with the Fermi Large Area Telescope. They are among the nearest molecular cloud complexes, within ~300 pc from the solar system. The γ-ray emission produced by interactions of cosmic rays (CRs) and interstellar gas in those molecular clouds is useful to study the CR densities and distributions of molecular gas close to the solar system. The obtained γ-ray emissivities above 250 MeV are (5.9 ± 0.1stat+0.9–1.0sys) × 10–27 photons s–1 sr–1 H-atom–1, (10.2 ± 0.4stat+1.2–1.7sys) × 10–27 photons s–1 sr–1 H-atom–1, and (9.1 ± 0.3stat+1.5–0.6sys) × 10–27 photons s–1 sr–1 H-atom–1 for the Chamaeleon, R CrA, and Cepheus and Polaris flare regions, respectively. Whereas the energy dependences of the emissivities agree well with that predicted from direct CR observations at the Earth, the measured emissivities from 250 MeV to 10 GeV indicate a variation of the CR density by ~20% in the neighborhood of the solar system, even if we consider systematic uncertainties. The molecular mass calibrating ratio, X CO = N(H2)/W CO, is found to be (0.96 ± 0.06stat+0.15–0.12sys) × 1020 H2-molecule cm–2 (K km s–1)–1, (0.99 ± 0.08stat+0.18–0.10sys) × 1020 H2-molecule cm–2 (K km s–1)–1, and (0.63 ± 0.02stat+0.09–0.07sys) × 1020 H2-molecule cm–2 (K km s–1)–1 for the Chamaeleon, R CrA, and Cepheus and Polaris flare regions, respectively, suggesting a variation of X CO in the vicinity of the solar system. From the obtained values of X CO, the masses of molecular gas traced by W CO in the Chamaeleon, R CrA, and Cepheus and Polaris flare regions are estimated to be ~5 × 103M ☉, ~103M ☉, and ~3.3 × 104M ☉, respectively. A comparable amount of gas not traced well by standard H I and CO surveys is found in the regions investigated.
    The Astrophysical Journal 08/2012; 755:22. · 6.28 Impact Factor

Publication Stats

6k Citations
1,284.42 Total Impact Points


  • 1979–2014
    • University of California, Santa Cruz
      • • Institute for Particle Physics
      • • Department of Astronomy and Astrophysics
      Santa Cruz, California, United States
  • 2009–2012
    • Politecnico di Bari
      Bari, Apulia, Italy
    • Stockholm University
      • Department of Physics
      Tukholma, Stockholm, Sweden
  • 2006–2012
    • INFN - Istituto Nazionale di Fisica Nucleare
      Frascati, Latium, Italy
  • 2000–2012
    • Stanford University
      • Department of Physics
      Palo Alto, California, United States
  • 2011
    • University of Freiburg
      • Faculty of Mathematics and Physics
      Freiburg, Lower Saxony, Germany
  • 2010
    • Max Planck Institute for Extraterrestrial Physics
      Arching, Bavaria, Germany
    • University of Maryland, College Park
      • Department of Astronomy
      Maryland, United States
    • University of Denver
      • Department of Physics and Astronomy
      Denver, Colorado, United States
    • Hiroshima University
      • Division of Physical Sciences
      Hirosima, Hiroshima, Japan
  • 2002–2009
    • Loma Linda University
      • Department of Radiation Medicine
      Loma Linda, CA, United States
  • 2005
    • University of Florence
      Florens, Tuscany, Italy
  • 2003
    • University of Padova
      Padua, Veneto, Italy
    • State University of New York
      New York City, New York, United States
    • Stony Brook University
      • Department of Computer Science
      Stony Brook, NY, United States
  • 1996
    • Okayama University
      • Department of Physics
      Okayama, Okayama, Japan
  • 1993
    • CSU Mentor
      Long Beach, California, United States
  • 1990
    • University of Washington Seattle
      • Department of Physics
      Seattle, Washington, United States
  • 1988
    • Los Alamos National Laboratory
      Los Alamos, California, United States
  • 1987–1988
    • University of Illinois, Urbana-Champaign
      • Department of Physics
      Urbana, Illinois, United States
  • 1976–1983
    • Princeton University
      • Department of Physics
      Princeton, NJ, United States
  • 1975
    • Istituto Universitario di Studi Superiori di Pavia
      Ticinum, Lombardy, Italy
    • University of Pavia
      • Department of Physics
      Pavia, Lombardy, Italy
  • 1973
    • Massachusetts Institute of Technology
      Cambridge, Massachusetts, United States
  • 1971
    • Deutsches Elektronen-Synchrotron
      Hamburg, Hamburg, Germany