B. Zhou

The L3 silicon microvertex detector

Abstract The design and construction of the silicon strip microvertex detector (SMD) of the L3 experiment at LEP are described. We present the sensors, readout electronics, data acquisition system, mechanical assembly and support, displacement monitoring systems and radiation monitoring system of the recently installed double-sided, double-layered SMD. This detector utilizes novel and sophisticated techniques for its readout.

An antimatter spectrometer in space

Abstract We discuss a simple magnetic spectrometer to be installed on a satellite or space station. The purpose of this spectrometer is to search for primordial antimatter to the level of antimatter/matter ≈10 −9 , improving the existing limits obtained with balloon flights by a factor of 10 4 to 10 5 . The design of the spectrometer is based on an iron-free, Ndue5f8Feue5f8B permanent magnet, scintillation counters, drift tubes, and silicon or time projection chambers. Different design options are discussed. Typically, the spectrometer has a weight of about 2 tons and an acceptance of about 1.0 m 2 sr. The availability of the new Ndue5f8Feue5f8B material makes it possible for the first time to put a magnet into space economically and reliably.

Limits on the antiproton/proton ratio in the cosmic radiation from 100 MeV to 1580 MeV

A search for antiprotons (p-bars) in the cosmic radiation with energies below 1580 MeV at the top of the atmosphere was performed using the PBAR balloon-borne magnetic spectrometer. No antiprotons were observed in 124,000 proton events. For the energy interval 100-640 MeV, an upper limit is reported to the p-bar/p ratio of 2.8 x 10 to the -5th at the top of the atmosphere, after correcting for instrumental efficiencies and contributions from secondary particles. No antiproton was observed in the energy interval 640-1580 MeV, which yields an upper limit to the p-bar/p ratio of 6.1 x 10. By combining both data sets, the limits on the p-bar/p ratio can be improved to 2.0 x 10 to the -5th. The detector performance and instrumental efficiencies of the individual detector components are discussed. A detail Monte Carlo calculation was used to evaluate the instrumental efficiency for both antiprotons and protons as a function of momentum. 48 refs.

The cosmic-ray He-3/He-4 ratio from 100 to 1600 MeV/amu

The Superconducting Magnet Instrument for Light Isotopes (SMILI) flew for 19 hours on September 1, 1989, with a residual overburden of 5 g/sq cm. It measured the charge, rigidity, and velocity of 30,000 cosmic-ray helium nuclei, with velocity determined by time-of-flight and Cerenkov techniques. Using these data, the flux and isotopic composition of helium as a function of energy were determined. The observed isotopic composition is consistent with that expected from interstellar propagation models inferred from the secondaries of CNO, in contrast to earlier observations which indicated an overabundance of He-3. We discuss constraints that this result places on cosmic-ray transport and solar modulation models.

The L3 Silicon Microvertex Detector: installation and results on 1993 performance

Abstract The status of the Silicon Microvertex Detector (SMD) and its installation into the LEP-L3 experiment are presented, highlighting novel features and sophisticated techniques. Preliminary results based on 1993 data are given and compared with Monte Carlo predictions, to understand the detector performances and its tracking capabilities.

A new generation gamma ray telescope

Abstract We describe the design of a ground based telescope which would be sensitive to extraterrestrial gamma rays with energies from 10 GeV to over 1000 GeV. Among other things, this telescope would enable the study of the emission mechanism of gamma rays from active galactic nuclei (AGNs), and of the interactions of gamma rays from AGNs with the intergalactic infrared radiation field (IIRF), possibly permitting an improved measurement of the Hubble constant. Calculations are presented which show that with the energy sensitivity and aperture of the telescope, as many as a thousand new sources of high energy gamma rays from outside of our Galaxy could be identified, about 10 of which would each be capable of measuring the Hubble constant to within 10% (assuming the parameters of the IIRF to be known).

PBAR: A superconducting magnet spectrometer for cosmic ray antiproton studies

Abstract We describe the PBAR balloon-borne magnet spectrometer flown on August 13–14, 1987 to measure the abundance of cosmic ray antiprotons in the energy interval 100–1580 MeV at the top of the atmosphere. The limits first reported [S.P. Ahlen et al., Phys. Rev. Lett. 61 (1988) 145] have been improved [M.H. Salamon et al., Astrophys. J. 349 (1990) 78] to an overall limit p / p − 5 (85% CL). We summarize the overall design and performance of the PBAR spectrometer, which had the unique ability to establish the mass of each singly charged cosmic ray, as well as to reject spurious antimatter candidates caused by hard scatterings within the instrument.

Using dimethylether as a drift gas in a high precision drift tube detector

Abstract Excellent spatial resolution (34 μm) has been obtained using dimethylether ((CH3)2O) at 1 atm in a small drift tube detector. This is better by at least a factor of 2 compared to previous work (∼ 80 μ m) with a conventional gas (a 50-50 argon-ethane mixture) in the same detector. The Lorentz angle and the gas amplification have been measured over a wide range of electric and magnetic fields.

Status of the L3 silicon microvertex detector

Abstract A report on the status of the construction of the L3 Silicon Microvertex Detector is presented here. The detector will consist of two double sided AC coupled silicon layers equipped with rφ and z readout with an expected intrinsic resolution of ≈ 6 μ m and ≈ 25 μ m respectively. A description of the detector with its mechanical support, alignment system and readout electronics is presented.

The L3 radiation monitor

Abstract A radiation monitoring system for the L3 experiment at the Large Electron Positron (LEP) collider is described. This system was installed in the L3 detector in April 1993. It provides information on the instantaneous and integrated radiation dose in the vicinity of the L3 silicon microvertex detector and time expansion chamber, and since April 1994 it has also provided trigger signals for the LEP beam dump in the case of large instantaneous dose rates in the L3 central tracking region.