M. Atac

Performance of multiclad scintillating and clear waveguide fibers read out with visible light photon counters

Abstract Measurements have been made of the performance of scintillating fibers read out with visible light photon counters (VLPCs). The light yields of single-clad and multiclad scintillating fibers have been compared. The experiment consisted of 3 m long scintillating fibers of 830 μm diameter optically coupled to 8 m long waveguide fibers of 965 μm diameter read out with HISTE-IV VLPCs. For the case of multiclad scintillating fiber and waveguide, an average of 6.2 photoelectrons was detected from the far end of the scintillating fiber if the fiber end was unmirrored, and 10.2 photoelectrons if the fiber end was mirrored. With this substantial photoelectron yield, minimum-ionizing tracks can be easily detected in fiber arrays, and excellent performance characteristics are expected for the fiber trackers designed for the D0 experiment at the Fermilab Tevatron Collider and the SDC experiment at the SSC Laboratory.

Measurements of drift velocities and Lorentz angles at 15 kG

We have measured the drift velocities and Lorentz angles of electrons in several candidate gases for the CDF central tracking chamber at magnetic fields of 10, 13.5, and 15 kG. The gases include argon/ethane (5050), argon/ethane/ethyl-alcohol mixtures, and argon/CO2/methane (89/10/1). For the preferred gas mixture of argon/ethane (5050) bubbled through alcohol at −7.2°C, we studied the sensitivity of the drift velocities and Lorentz angles to changes in electric field, magnetic field, alcohol temperature, and argon/ethane ratio. Measurements with argon/methane (8020) at 5 and 10 kG are also presented.

Beam test results of the US-CMS forward pixel detector

Abstract CMS will use silicon pixel as its innermost tracking device. Prototypes of these 150 μm square pixels bump bonded to DMILL readout chips were tested at CERN in a pion beam. A silicon telescope consisting of 8 planes of silicon strips was used to interpolate tracks to the position of the pixel detector. Data were taken with the beam at different angles of incidence relative to the pixel sensors. Position resolutions between 10 and 20 μm , depending on the hit position, were observed using charge sharing for the final configuration with unirradiated detectors. The observed resolution was as expected.

A gas sampling calorimeter using conductive plastic tubes (II)

Abstract A prototype module for the electromagnetic shower calorimeter has been constructed and its characteristics have been measured. It consists of 38 layers of planar proportional chambers interleaved with 3 mm thick lead plates. The proportional chamber is made of conductive plastic tubes as a dc cathode and pickup electrodes as an rf cathode. The pickup electrodes are copper-clad G-10 panels etched with finely segmented patterns which, when assembled, form complete conical towers. The module was tested using high energy electron and hadron beams of energy range from 25 GeV to 150 GeV. Energy resolution is 24% E( GeV ) , and the position resolution is 1.5 mm or better at and above 50 GeV. The lateral and longitudinal distributions of the energy deposit are studied and they are applied to π e discrimination.

Radial Wire Drift Chambers for CDF Forward Tracking

Radial wire drift chambers have been built for the Collider Detector of Fermilab (CDF) to cover forward and backward cone angles between 20 and 100 and 170° and 178°. The chambers are built to provide good azimuthal track resolution, good multi-track resolutions, and high rate capability. Tests done using cosmic-rays and nitrogen UV-laser beam show that single wire resolution of 110 ¿m and 68 ¿m are obtainable, respectively. Construction details and test results are presented.

Radiation hardness studies of cooling fluids epoxies and capacitors for CMS pixel system

Abstract Radiation hardness studies of C6F14 Fluorinert (FC72) fluid, some epoxies and tantalum capacitors were studied for the Compact Muon Solenoidal (CMS) experiment at the Large Hadron Collider (LHC) of CERN. For a successful operation of Forward Silicon Pixel Tracker of the CMS, the cooling fluid, epoxies to be used and the filter capacitors of bias voltage supplies need to be radiation hard. It was also necessary to find out whether the cooling fluid would dissociate under the expected fluence and damage beryllium cooling channels of the Forward Silicon Pixel Discs. This paper is a report of our findings from the performed tests.

A fast ring-imaging Cherenkov counter for a fixed-target heavy-quark experiment

We present a design for a fast ring-imaging Cherenkov counter operating in the visible. The Cherenkov photons are imaged on an array of small Winston cones and read out with optical fibers and VLPCs. the design is optimized for {pi}/K/p separation in the range 10 < p < 100 GeV/c.

Radial Drift Chambers Fop CDF Forward Tracking

Radial wire drift chambers are built for the Collider Detector of Fermilab to cover forward and backward regions between 2° and 10° cones which will provide good azimuthal position information of tracks, good multi-track, and high rate capability. Results obtained from a prototype chamber show ¿ resolution of ¿rms ¿ 130 ¿m and a charge division accuracy of 0.7 percent along the wire (¿,r) running in the saturated avalanche mode.

π/e separation with prototype CDF end plug gas calorimeters

Hadron rejection against electron signal of a combined system of electromagnetic and hadron calorimeter has been studied. Data was taken at M4 beam line of Fermilab at energies from 25 GeV to 150 GeV. Hadron rejection of electromagnetic calorimeter is greatly improved by the use of hadron calorimeter information. The details of the results are discussed.