M. Vigneault

Studies of wavelength-shifting liquid filled quartz capillaries for use in a proposed CMS calorimeter

Studies have been done and continue on the design and construction of a Shashlik detector using Radiation hard quartz capillaries filled with wavelength shifting liquid to collect the scintillation light from LYSO crystals for use as a calorimeter in the Phase II CMS upgrade at CERN. The work presented here focuses on the studies of the capillaries and liquids that would best suit the purpose of the detector. Comparisons are made of various liquids, concentrations, and capillary construction techniques will be discussed.

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.

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.

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.

Studies of the pattern of light emitted from waveshifting, scintillating, and waveguide fibers used in detectors for particle physics

Scintillating, waveshifting, and waveguide fibers are used as particle detectors and light detection and transport elements in particle physics experiments. A study of light emission from such structures is being carried out for the Compact Muon Solenoid (CMS) experiment at CERN. For CMS, the fibers used are polystyrene core with a double-cladding and a diameter of 940 microns and lengths of up to several meters. Currently, the light produced and transported by such structures is detected by a conventional photo-detectors called hybrid photodiodes (HPD). The experiment is planning to replace the HPDs with a new photo-detectors known as a Silicon Photomultipliers (SiPM) with the possibility of each fiber having its own SiPM element for readout. Due to the thermal and electrical characteristics of SiPMs, and specifically their high thermal noise rate, it is best to keep the cross sectional area of the SiPM as small as possible. When light exits a fiber there is a distribution of the photons at various angles caused by: the differences in index of refraction of the core (n=1.59) and outer cladding (n=1.43) of the fiber; how and where in the fiber the initial light was created and the dominant transmission characteristics of the fiber/waveguide. This light distribution sets the size and placement of the SiPM devices. To study this, experimental measurements are being carried out using waveshifting and clear optical waveguide fibers that are used in CMS. Light is produced within such fiber core by exciting them through their cladding using UV light emitting diodes (LEDs). The LED light penetrates into the fiber and is waveshifted. On one end (called the readout end) is placed up against a fiber-optically-coupled CCD camera. The opposite end is either mirrored (with aluminum) or unmirrored and also read out using another CCD. Initial studies of attenuation and the profile of emergent light are discussed.

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.

A cosmic ray detector telescope for use in informal and formal education settings

We have developed an orientable cosmic ray telescope based on scintillating tile and waveshifting optical fiber technology for hands-on laboratory use and for interactive public displays. The device is sensitive to ionizing radiation and is composed of four individual scintillating tiles into which are embedded double-clad optical fibers doped with waveshifter dye. These fibers are coupled to photomultiplier tubes (PMT). The telescope is mounted on an adjustable (rotatable) structure to allow the measurement of the cosmic ray rate as a function of angle relative to the zenith. This motion is controlled by the user through a computer-controlled stepper motor. The readout system allows data to be collected and uploaded to the Web enhancing the interactive experience and for follow-up analysis.

FAST, LONG-WAVELENGTH SCINTILLATORS AND WAVESHIFTERS

Studies are presented of new blue-green to red emitting scintillator and waveshifter materials for tracking and calorimetry applications for the detection of ionizing radiation. Materials include plastic scintillators, liquid scintillators, and plastic scintillating and waveshifting fibers. Program goals are to develop faster and more efficient detection media for a variety of experimental applications

Fast, long-wavelength scintillators and waveshifters

Studies are presented of new blue-green to red emitting scintillator and waveshifter materials for tracking and calorimetry applications for the detection of ionizing radiation. Materials include plastic scintillators, liquid scintillators, and plastic scintillating and waveshifting fibers. Program goals are to develop faster and more efficient detection media for a variety of experimental applications

Waveshifters and scintillators for the detection of ionizing radiation

New waveshifter and scintillator materials are under development for use in detecting charged particles in tracking applications and for detecting showering particles in calorimetric applications. Goals have been to identify and produce fast and efficient dye materials that fluoresce in the middle of the visible spectrum where polystyrene and polyvinyltoluene have good optical transparency, to replace existing materials currently in use in the field of particle physics. As a result of this study, several fluorescent dyes have been identified with fast and efficient emission, that fluorescence in the green (/spl lambda/ /spl sim/ 490-520 nm), and from these a number waveshifter and scintillator materials have been fabricated.