S. V. Somov

A drift detector system with anode and cathode readout in the GlueX experiment

A drift detector system designed to detect charged particle tracks in the GlueX experiment dedicated to study the nature of confinement is described. The key design features of the drift chambers associated with the requirement of a minimum material budget in the path of secondary particles are presented. The spatial resolution and the detection efficiency have been measured with cosmic rays using the automatic data acquisition system.

A 250 MHz Level 1 Trigger and Distribution System for the GlueX experiment

The GlueX detector now under construction at Jefferson Lab will search for exotic mesons though photoproduction (10^8 tagged photons per second) on a liquid hydrogen target. A Level 1 hardware trigger design is being developed to reduce total electromagnetic (≪ 200 MHz) and hadronic (≫ 350 kHz) rates to less than 200 kHz. This trigger is deadtimeless and operates on a global synchronized 250 MHz clock. The core of the trigger design is based on a custom pipelined flash ADC board that uses a VXS backplane to collect samples from all ADCs in a VME crate. A custom switch-slot board called a Crate Trigger Processor (CTP) processes this data and passes the crate level data via a multi-lane fiber optic link to the Global Trigger Processing Crate (also VXS). Within this crate detector sub-system processor (SSP) boards can accept all individual crate links. The subsystem data are processed and finally passed to global trigger boards (GTP) where the final L1 decision is made. We present details of the trigger design and report some performance results on current prototype systems

Recording of relativistic particles in thin scintillators

Results of investigating an assembly of thin scintillators and silicon photomultipliers for registering relativistic particles with the minimum ionization are presented. A high efficiency of registering relativistic particles using an Ej-212 plastic scintillator, BSF-91A wavelength-shifting fiber (Saint-Gobain), and a silicon photomultiplier (Hamamtsu) is shown. The measurement results are used for creating a scintillation hodoscope of the magnetic spectrometer for registering γ quanta in the GlueX experiment.

Time characteristics of detectors based on silicon photomultipliers for the GlueX experiment

Silicon photomultipliers (SiPMs) are used in detectors of the GlueX experiment devoted to studying the nature of confinement. These detectors are operable at counting rates as high as 2 MHz with a time resolution (FWHM) of approximately 0.3 ns and a number of excited pixels of up to 104. For SiPMs that operate under these conditions, the measured dependences of the recovery time and the time resolution are presented as functions of the number of excited pixels and the excitation frequency. Using a picosecond laser, the time resolution has been measured for an array of 4 × 4 SiPMs, which was specially developed for the experiment.

Performance of the pair spectrometer of the GlueX experiment

The description of the pair spectrometer of the GlueX detector at Jefferson Lab and its performance during the first beam commissioning runs are presented. We measured the amount of light collected from each channel of the pair spectrometer hodoscopes and the time resolution of the pair spectrometer counters.

Calibration of cathode strip gains in multiwire drift chambers of the GlueX experiment

A technique for calibrating cathode strip gains in multiwire drift chambers of the GlueX experiment is described. The accuracy of the technique is estimated based on Monte Carlo generated data with known gain coefficients in the strip signal channels. One of the four detector sections has been calibrated using cosmic rays. Results of drift chamber calibration on the accelerator beam upon inclusion in the GlueX experimental setup are presented.

Time characteristics of silicon photomultipliers used in the GlueX experiment

The GlueX detector in Hall D at Jefferson Lab is instrumented with about 5000 Silicon Photomultipliers (SiPM) manufactured by Hamamatsu Corporation. Silicon photomultipliers with a sensitive area of 3×3 mm2 are used to detect light from scintillator detectors such as: the tagger microscope, pair spectrometer, and start counter. An array of 4×4 SiPM sensors was specially designed by Hamamatsu for the instrumentation of the barrel electromagnetic calorimeter. SiPMs in the tagger microscope and start counter will be operated at a relatively large rate of up to 2 MHz. We performed measurements of the time resolution for different SiPM operation rates and estimated the SiPM recovery time. Time characteristics were compared for sensors with two pixel sizes: 25 μm (MPPC S10362-33-025C, MPPC S10931-025P) and 50 μm (MPPC S10362-33-050C, MPPC S10931-050P). Time resolution of the SiPM array (MPPC S12045) was measured as a function of light for several SiPM temperatures. Studies were performed using a picoseconds laser light pulser and a light-emitting diode.