B. Buck

The OLYMPUS experiment

OLYMPUS is an experiment mounted by an international collaboration at DESY, Hamburg, Germany to provide a ±1% measurement of the cross section ratio of positron-proton to electron-proton elastic scattering in the range 0.6 < Q2 < 2.2 (GeV/c)2. The goal is to provide a definitive experimental verification of the generally accepted explanation of the discrepancy between cross-section and recoil polarization techniques in determination of the form factor ratio GEp(Q2)/GMp(Q2).

Improving Photoelectron Counting and Particle Identification in Scintillation Detectors with Bayesian Techniques

Many current and future dark matter and neutrino detectors are designed to measure scintillation light with a large array of photomultiplier tubes (PMTs). The energy resolution and particle identification capabilities of these detectors depend in part on the ability to accurately identify individual photoelectrons in PMT waveforms despite large variability in pulse amplitudes and pulse pileup. We describe a Bayesian technique that can identify the times of individual photoelectrons in a sampled PMT waveform without deconvolution, even when pileup is present. To demonstrate the technique, we apply it to the general problem of particle identification in single-phase liquid argon dark matter detectors. Using the output of the Bayesian photoelectron counting algorithm described in this paper, we construct several test statistics for rejection of backgrounds for dark matter searches in argon. Compared to simpler methods based on either observed charge or peak finding, the photoelectron counting technique improves both energy resolution and particle identification of low energy events in calibration data from the DEAP-1 detector and simulation of the larger MiniCLEAN dark matter detector.

A readout system utilizing the APV25 ASIC for the Forward GEM Tracker in STAR

We have developed a modular readout system for the 30,720 channel Forward GEM Tracker recently installed in the STAR Experiment at RHIC, BNL. The modular architecture is based on a passive compact PCI backplane running a custom protocol, not PCI, connecting 6 readout modules to a readout controller module. The readout modules provide all necessary functions, including isolated power supplies, to operate up to 24 APV25 chips per module with high-impedance ground isolation. The front-end boards contain a minimal set of components as they are located inside the STAR TPC inner field cage and are inaccessible except during long shutdown periods. The front-end boards connect to the readout modules with cables up to 24 m in length, carrying unbuffered analog readout signals from the APV25 as well as power, trigger, clock and control. The readout module digitizes the APV analog samples to 12 bits at 37.532 MHz, and zero suppresses and buffers the data. The readout controller distributes trigger and clock from the central trigger system, gathers the data over the backplane, and ships it to a linux PC via a 2.125 Gbps optical data link (Detector Data Link (DDL) from ALICE). The PC gathers data from multiple readout controllers and dispatches it to the STAR event builders. The readout modules, controllers, and backplanes are housed in a common crate together with the GEM HV bias power supplies.

Design of the MiniCLEAN dark matter search veto detector subsystem

Abstract This paper describes the design of the active muon veto subsystem for the MiniCLEAN dark matter direct detection experiment at SNOLAB in Sudbury, Ontario, Canada. The water-filled veto is instrumented with 48 PMTs which are read out by front-end electronics to time multiplex 48 photomultiplier channels into 6 digitizer channels and provide an instantaneous hit sum across the subsystem (N-Hit) for the veto trigger. We describe the primary system components: the PMTs, the support structure, the front-end electronics, and the data acquisition system.

Heavy-Ion Testing Results for Several Commercial and Military Grade Parts

We report the results of testing seven components for single event effects at the 88-inch Cyclotron at Lawrence Berkeley National Laboratory.