Gregory Tarle

Track‐recording solids

Since the beginning of the solar system, natural particle detectors have been recording the passage of charged particles from the sun and cosmic rays. Now, in addition to developing the latent images of these fossil trails of damage in solids and learning about the nature of ancient radiation, we are creating new and more sensitive detectors of a similar kind. These detectors, which are finding a wide variety of applications, take advantage of the fact that a highly charged particle penetrating any nonconducting solid leaves a submicroscopic trail that can be chemically amplified. The increased chemical reactivity of the trails of radiationdamaged material is the basis for the so‐called etched‐track process, by which we make the particle tracks large enough to measure in an optical microscope. As we will see, there is sufficient information in the tracks to allow us to determine a particles charge and velocity.

Effect of electron capture and loss on the response of polycarbonate track detectors to relativistic uranium ions

Abstract The effect of electron capture and loss on the response of polycarbonate track detectors to relativistic, ultraheavy ions is considered. Data from plastics exposed to ∼1 GeV/u 238 U at LBLs Bevalac demonstrates the attainment of one-quarter charge unit resolution in the actinide region, by using a couple of methods discussed here to diminish the effect of a broad charge state distribution of the heavy ion.

Studies of Relativistic Uranium Nuclei with Dielectric Track Detectors

The cross section for the breakup of relativistic uranium projectiles (energy ∼ 35 billion electron volts) into two large fragments in the track detector CR-39 was measured and found to be about half of the geometric cross section. The range of the uranium projectiles was also measured and found to agree with that predicted by the Bethe theory when modified to account for the capture of orbital electrons by the projectiles.

An antinucleus detector with unprecedented collecting power and resolution

Abstract We describe the details of a novel technique to detect the presence of antimatter in cosmic rays by taking advantage of the presence of higher order quantum electrodynamic effects involving the interactions of relativistic, heavily ionizing particles with plastic scintillators, track etch detectors and Cherenkov counters. We review the relevant physics, summarize the experimental status involving the response mechanisms of the different types of particle detectors, and give a detailed description of the construction and anticipated performance characteristics of the instrument. By extending the sensitivity of previous antimatter searches by two orders of magnitude, this experiment should be the first to be sensitive to extragalactic antimatter, should the universe contain substantial quantities of antimatter.

Integration and testing of the DESI multi-object spectrograph: performance tests and results for the first unit out of ten

The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 deg² will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. A consortium of Aix-Marseille University (AMU) and CNRS laboratories (LAM, OHP and CPPM) together with LPNHE (CNRS, Universities Pierre et Marie Curie and Paris-Diderot) and the WINLIGHT Systems company based in Pertuis (France), are in charge of integrating and validating the performance requirements of the full spectrographs. This includes the cryostats, shutters and other mechanisms. The first spectrograph of the series of ten has been fully tested and the performance requirements verified for the following items: focus, image quality, straylight, stability, detector properties and throughput. We present the experimental setup, the test procedures and the results.

DESI fiber positioner testing and performance

The Dark Energy Spectroscopic Instrument (DESI) is under construction to determine the expansion history of the Universe using the Baryon Acoustic Oscillation technique. Over the life of the experiment DESI will measure the spectra of 35 million galaxies and quasars over 14,000 square degrees out to a redshift of 3.5. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5,000 robotic fiber positioners located at the prime focus. The fibers in turn will feed ten broad-band spectrographs covering the wavelength range from 360nm to 980 nm. Rapid and accurate targeting of the fibers is provided by precision theta-phi robotic fiber positioners. The fiber positioners are manufactured at the University of Michigan. Following assembly each positioner passes through a burn-in and verification sequence. We describe the testing of the positioners and discuss the performance achieved.