W. Kononenko

Performance of the SiGe HBT 8HP and 8WL technologies after high dose/fluence radiation exposure

An assessment of the radiation tolerance of the latest generation IBM silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) technologies (SiGe 8WL and SiGe 8HP) at extreme dose/fluence is reported. These BiCMOS technologies are of great interest for analog readout circuits in high energy physics detectors, especially the planned upgrade of the ATLAS detector for the upgraded Large Hadron Collider (sLHC) in Geneva, Switzerland. These third-generation, 130 nm SiGe HBTs show promise to operate at lower power than CMOS circuits provided that they can be shown to be sufficiently radiation tolerant. This study presents evidence of the radiation tolerance of these two candidate technologies with parametric measurements after irradiation up to a fluence of 1016 1 MeV equivalent neutrons/cm2 and a gamma dose of 100 Mrad (SiO2).

Front end electronics for the CDF-II Time-of-Flight system

A Time-of-Flight detector (TOF) has been added to the CDF-II experiment to provide charged kaon identification primarily for neutral B meson flavor determination. The TOF front end electronics system has 432 channels and is designed to run at the 7.58 MHz bunch crossing rate in CDF. The electronics contributes less than 25 ps to the anticipated TOF timing resolution of 100 ps, which is dominated by photon statistics. This paper describes the design and implementation of the electronics as well as the initial in situ performance.

Cherenkov and Scintillation Light Measurements with Scintillating Glass, SCG1C

We have been able to observe and measure both the direct Cherenkov (C) and the Scintillation (S) light components from scintillating glass, distinctly separated in time. This has important implications for hadron calorimetry, electron/hadron separation and low energy particle identification.

Scintillator-waveshifter light measurements

Abstract A series of measurements is presented on the number of photoelectrons produced and the attenuation using a series of new scintillators and waveshifter materials. Possible applications are mentioned.

Evaluation of Two SiGe HBT Technologies for the ATLAS sLHC Upgrade

As previously reported, silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) technologies promise several advantages over CMOS for the front-end readout electronics for the ATLAS upgrade. Since our last paper, we have evaluated the relative merits of the latest generations of IBM SiGe HBT BiCMOS technologies, the 8WL and 8HP platforms. These 130nm SiGe technologies show promise to operate at lower power than CMOS technologies and would provide a viable alternative for the Silicon Strip Detector and Liquid Argon Calorimeter upgrades, provided that the radiation tolerance studies at multiple gamma and neutron irradiation levels, included in this investigation, show them to be sufficiently radiation tolerant.

Performance of a dual-layer positron-sensitive surgical probe

A positron-sensitive surgical probe is being built based on a multi-anode PMT and a dual-layer detector, which consists of an 8/spl times/8 array of thin plastic scintillators and a matched GSO crystal array. Our probe uses three selection criteria to identify positrons and suppress background gammas, including annihilation 511 keV gammas. First an energy threshold was applied on the plastic signals; next a second energy threshold was applied on the PMT sum signal; finally, a coincidence technique between the positrons and the annihilation 511 keV gammas was applied. These selection criteria were individually tested and optimized, and have been implemented with 9 channels of electronics. Experiments were conducted using phantoms with /sup 18/F-FDG and /sup 99m/Tc, commonly used in sentinel lymph node (SLN) surgery. Measurements based on the 9-channel electronics indicate that the sensitivity of the 9-channel probe to positrons from /sup 18/F-FDG is /spl sim/69-152 cps/kBq (2.5-5.6 kcps//spl mu/LCi) at different signal selection criteria The final 64-channel probe is expected to have /spl sim/40% higher positron sensitivity. The pixel separation is /spl sim/3.2 in terms of the peak to valley ratio. The second layer of the detector gives superior rejection power for 140 keV gammas. The true to false positron count ratio in the presence of 511 keV and 140 keV background gammas is expected to be high (>10) at a tumor to background ratio of 10:1.

Signal and Noise Measurements for Muons in Scintillating Glass with Vacuum Photodiode Readout

We have been able to measure 6 photoelectrons per MeV of energy loss in scintillating glass, SCG-1, using large area vacuum photodiodes for readout with a signal to noise ratio of about 4.5.

A 64-pixel positron-sensitive surgical probe

We report on the continued development of a 64-pixel positron-sensitive surgical probe with a dual-layer detector and a multi-anode PMT. An 8 /spl times/ 8 array of thin plastic scintillators in the first layer detects positrons and a matched GSO crystal array in the second layer detects annihilation 511 keV gammas, which are required to be in coincidence with the detected positrons. Also, the 64 PMT anode signals are differentiated and an overshoot threshold is applied to separate the fast decay plastic anode signals from the slower GSO anode signals. Finally, an energy threshold is applied to the summed anode signal to distinguish 511 keV gammas from the 140 keV gammas commonly used in sentinel lymph node (SLN) surgery. Previously we reported on how these signal selection criteria were individually tested and optimized based on 9 channels of prototype electronics. Currently the electronics have been upgraded to Xilinx/spl reg/ programmable components, allowing on-the-fly alteration of signal selection criteria, and all 64 channels are operational. Initial measurements of the complete 64-pixel probe were conducted using /sup 18/F-FDG positron sources and /sup 18/F-FDG and /sup 99m/Tc phantoms (background 511 keV and 140 keV gammas), simulating lesions in the SLN surgery environment. The average positron sensitivity is measured to be 3.0-7.0 kcps//spl mu/Ci at different signal selection criteria. The lower bound on sensitivity corresponds to settings optimized for high image resolution and high background rejection ability. The upper bound on sensitivity corresponds to settings optimized for high sensitivity at the cost of lower image resolution and lower background rejection ability. The measured true-to-background contrast in the presence of clinically observed levels of 511 keV and 140 keV background gammas is /spl sim/3:1 for a tumor-to-background uptake ratio of 5:1. Performance measurements of the complete 64-pixel probe including sensitivity, true-to-background ratio, and the pixel separation ability are presented.

Silicon microstrip electronics operating with 20 ns FWHM signals

For experiment E771 at Fermilab, semicustom integrated circuit (IC) preamplifiers and discriminators have been designed to operate at near single-bucket speed, i.e. to give signals, from a silicon microstrip detector (SMD), shaped to 15 or 20 ns FWHM. Measurements of signal size, signal-to-noise ratio (SNR), and noise rate and signal efficiency versus discriminator threshold setting were made. The test setup used an SMD plane 300- mu m thick with 50- mu m strips and the prototype ICs produced for experiment E771. Signals were produced by near-relativistic beta rays. The test setup had somewhat larger detector capacitance (C/sub d/ approximately=25 pF) than the final experiment detector will have. For tracks passing through the SMD plane nearly perpendicularly, good efficiency was found at acceptable noise rates. When the signal comes almost entirely from a single strip, the SNR is about eight to one. Under these conditions, when the discriminator threshold is set to give about 0.001 to 0.002 noise hits per strip per trigger, the latching efficiency is above 95%. For tracks at an appreciable angle from perpendicular, the deposited charge is shared between strips. For tracks with 60% of the charge or more in a single strip, the efficiency is well over 90%. >

A prototype sampling calorimeter with photodiode readout (SPED)

We have built and tested a new type of sampling calorimeter using scintillator as the active material, and thin vacuum photodiodes for signal readout, the new feature. We measure an energy resolution of about 22%/✓E for electrons of 10–37.5 GeV. For muons the signal to noise ratio is about 2.4, corresponding to about 1000 pe/cm of scintillator. Important merits of such a design such as the excellent gain stability (photodetector gain=1), absence of the need for high voltages, and system simplicity in construction and operation, have been demonstrated.