C. Bolon

A Spherical Drift Chamber Area Detector for X-Ray Crystallography

A multiwire proportional chamber system has been built as an area detector for use in x-ray crystallography with Cu K¿ radiation (1.54Å). The chamber, constructed by Charpak and collaborators at CERN, consists of a 10cm thick spherical interaction region with a radial electric field, a transition from spherical to plane geometry and a 50cm × 50cm multiwire proportional chamber and subtends a 90° opening angle. Two dimensional position information is obtained from orthogonal cathode planes using a high speed analog centroid finding technique. Data on spatial and energy resolution as a function of angle and depth of interaction in the spherical drift region using a collimated, pulsed, x-ray source are presented. Ionization loss as a function of drift distance and field and loss due to field shaping grids has also been measured.

Pressurized Xenon-Filled Multiwire Proportional Chamber for Radionuclide Imaging

A pressurized multiwire proportional chamber radionuclide imaging system has been constructed which has operated at pressures of up to 11 atmospheres absolute using a xenon-methane gas mix. The experimental detector has an active imaging area of 25 sq. cm. and an effective depth of 11 cm. An all digital readout system has been constructed with an intrinsic resolution of 1.3 mm FWHM. The FWHM has been measured for various radionuclides: iodine-125 (28 keV), 1.3 mm; thallium - 201 (75 keV), 2 mm; technetium-99 m (140 keV), 3 mm. Our primary goal has been the investigation of properties of such detectors that offer advantages over conventional gamma cameras, including high data rate and improved spatial resolution, particularly for isotopes with photon energies below 100 keV. We have fabricated a gas purification system which permits long term operation of the system without degradation and have investigated construction techniques to produce reliable devices which could be used in a hospital environment.

X-Ray Crystallography Using a Spherical Proportional Camera

A wide angle gas proportional detector specifically designed for X-ray crystallography has been instrumented and is being applied in pilot experimental studies. It has essentially complete efficiency, uniform spatial precision of 2 mrad FWHM, acceptance over 90 degrees, and count rate capability to 100,000 per second at less than 10% loss. Comparison of data with conventional measurements indicates satisfactory angular mappings and a relative R-factor for scaled intensities of better than 10%.

Proportional Chamber Data Acquisition Providing Maximum Spatial Resolution at High Rates

A proportional chamber readout system designed to provide maximum spatial resolution in two-dimensional images acquired at high data rates has been designed and constructed. This system has been tested on a spherical drift chamber area detector, described in another report at this conference, and it has yielded an image resolution of 0.4 mm FWHM at a count rate of 100,000 events per second in a finely collimated pencil beam. The ultimate resolution believed to be possible with the readout is about 0.2 mm FWHM, and the incident rate at which degredation of resolution occurs is expected to be in excess of 500,000 events per second. The readout is based on acquiring analog signal levels in time intervals comparable to the current pulses on anode wires, then processing these signals with high speed analog circuits and digitizing the result. The present system uses 80 parallel channels on each coordinate of a 50 cm square image area, has a total acquisition time of as little as 70 ns, and provides a throughput rate of up to 200,000 events per second.

Particle ratios in inclusive electroproduction from hydrogen and deuterium

Abstract We present a high statistics study of particle ratios in electroproduction of forward hadrons. The π + / π − ratios for a proton target rise monotonically to a value of 2.4 ± 0.2 at Q 2 of 3 (GeV/ c ) 2 and for a neutron target average 1.16 ± 0.04 from Q 2 of 0.35 to 3 (GeV/ c ) 2 . We report the first data on electroproduction of p , and measure the cross sections of K ± , p, and p relative to pions as a function of Q 2 .

Muon pair photoproduction at 20.5 GeV

Abstract We have studied the production of muon pairs with invariant masses from 1 to 4 GeV by 20.5 GeV bremsstrahlung radiation. The invariant mass distribution has a large deviation from the expected Bethe-Heitler shape which we attribute to the ψ (3.1 GeV). We determine the ψ (3.1 GeV) photoproduction cross section to be 3.7 −1.5 +2.2 nb at an average photon energy of 18 GeV.

Charge correlations in electroproduction of hadrons

Using electroproduction data, we have measured the charge ratio of residual hadron yields given a fixed-charge leading hadron. We find this ratio to favor unlike charges and to depend principally on p/sub l//p/sub l/max of the residual hadrons. The two possible ratios are not charge symmetric. We also deduce that our result is not primarily a manifestation of charge conservation.