J. Marchant

Studies of SiPM and Scintillation Plates with waveshifter fiber and SiPM readout

We have been studying the performance of SiPM devices and Scintillation Plates read out with SiPM. Applications are for the detection of ionizing radiation, for example in particle and nuclear physics experiments. Results are presented on performance of the SiPM using pulsed LEDs and scintillating tiles excited by radioactive sources, and for SiPM devices that have been used to transduce waveshifted scintillation signals from scintillation tiles with embedded waveshifter fiber.

Small cryostem for operation of Visible Light Photon Counters (VLPC)

We have designed, constructed, and operated a small cryostem which supports the operation of 32 channels of visible light photon counters (HISTE-IV VLPCs). The VLPCs are situated within a small enclosure which can be lowered into a 30-100 liter dewar. The enthalpy of the boil-off helium keeps the VLPCs cold, and allows the system to be operated with stability for many days within the desired temperature range of 6.0 K-7.5 K. The cryostem is instrumented with clear fiber waveguides which transport the light from an optical connector situated at the top of the cryostem and outside of the dewar to the photosensors at cryogenic temperatures within the dewar. Electrical signals from the VLPCs are amplified at room temperature using QPA02 preamplifiers. Details of design and performance are reviewed.

Liquid-based scintillators for particle physics

Preliminary results are presented of a study of organic liquid-based scintillators. The objectives of the study were to identify materials that have good spectral characteristics the match state of the art solid state photosensors such as SiPM devices, high quantum efficiency, rapid fluorescence decay and good handling and safety characteristics. Potential applications for such materials are in high radiation environments in forward-calorimetry in colliding beam experiments and for active instrumentation in large volume applications, such as underground experiments.

A portable cosmic ray detector and display

We have developed a hand-held, particle tracking detector based on scintillating-glass, fiber-optic plate technology for applications in classroom teaching. The active element is sensitive to ionizing radiation and is a coherent fiber-optic plate consisting of 10/sup 6/ individual clad fiber waveguides that contain Terbium (3+) oxide in a silicate glass host. Scintillation light in the individual fiber elements is transferred via total internal reflection to a multi-stage image intensifier that senses and amplifies the light signal while maintaining the spatial coherence of the input optical image. The output screen of the image intensifier can be viewed directly by eye under low-level room light conditions or via video imaging with a CCD camera. The system is ideal for hands-on laboratory use and for public lecture demonstrations.

Calibration system for the 3072 channel scintillating fiber/VLPC test facility for the D0 upgrade at Fermilab

A calibration system for the testing of scintillating fibers and visible light photon counters (VLPC) has been constructed at Notre Dame and installed in a cosmic ray test facility at Fermilab. The purpose of the cosmic ray test is to assess the viability of the fiber tracking technique for the upgraded D0 central detector. The purpose of this calibration system is to monitor the performance of the 3072 fiber VLPC detector elements for continuity, gain and uniformity of response. Here we report on the design, construction and operation of the calibration system. >

PVT scintillators with very-high fluorescent dye concentrations

A concentration study of the fluorescent dye pyrene in bulk PVT-based scintillator is the subject of this investigation. Pyrene is known to form an excimer at elevated concentration, with fluorescence properties quite distinctive from that of individual pyrene molecules. The fluorescence excitation, emission, decay time, and scintillation efficiency have been studied over an extensive concentration range, from 5g/l to 225g/l. We observe a significant decrease in fluorescence decay time and an increase in fluorescence efficiency with increasing pyrene concentration. At highest concentration, a light yield of 84% of EJ-201T is obtained.

Production of optical decoder units for the CMS Hadron Calorimeter

The CMS Hadron Calorimeter (HCAL) will use optical decoder units (ODU) as a link between scintillating plastic tiles, arranged in megatile layers around the HCAL, and multi-channel hybrid photodiodes. Photons are produced in the scintillating tiles as sub-atomic particles pass through and deposit energy. Y-11 waveshifting fiber and cables of clear optical fiber serve as connecting transmission lines from scintillating tiles to the ODU. The ODU reorganizes light signals from layer geometry to tower geometry for particle energy measurement. The hybrid photodiode (HPD) converts the light signals to electrical signals that are amplified and digitized for the data acquisition system. This paper provides aspects of the production of optical decoder units.

Calibration system for the Central Fiber Tracker for the D0 Upgrade

We are developing a calibration system for the Central Fiber Tracker (CFT) for the D0 Upgrade to monitor the optical integrity, channel gain, and gain stability for the 76,000 fiber channels with VLPC readout which comprise the system. Excitation is by blue Light Emitting Diodes (LEDs), with light distributed to the CFT fiber ribbons via luminous fiber panels. System design and performance will be presented.

Studies of optical mixers for use with silicon photomultipliers to ameliorate signal saturation

We have been studying ways in which the light from several optical fibers that transmit light from scintillating tiles can be mixed and combined a single Silicon Photo Multiplier (SiPM). The purpose for mixing is to prevent a single high intensity fiber from saturating an area of the SiPM and thus causing an inaccurate reading of the overall light collected. In particular this is for use in detectors such as CMS HCAL1, 2 where light is transmitted from scintillating tiles in 940,.m fibers to a single photo-detector. If one tile has a large optical signal it can saturate an area of the SiPM and produce a signal lower than would be expected, resulting in an in-accurate energy measurement. The results of the test and the test setup will be described.

Detection of ionizing radiation in coherent plates of scintillating plastic optical fibers

Fully functional imaging scintillating-glass fiber detectors have been fabricated by our group and operated successfully over many years. In this paper we present our initial efforts to produce coherent fiber-optic tracking detectors based upon organic plastic scintillating fiber materials. The goal is to create devices of relatively large volume that can be used in informal education settings and that likewise permit the imaging of trajectories of ionizing particles in real time as they pass through the material. To improve the rate of particle detection, coherent plates of sizeable volume (25mm × 25mm × 100mm or more) are desirable.