J.F. Amsbaugh

An array of low-background 3He proportional counters for the Sudbury Neutrino Observatory

An array of Neutral-Current Detectors (NCDs) has been built in order to make a unique measurement of the total active ux of solar neutrinos in the Sudbury Neutrino Observatory (SNO). Data in the third phase of the SNO experiment were collected between November 2004 and November 2006, after the NCD array was added to improve the neutral-current sensitivity of the SNO detector. This array consisted of 36 strings of proportional counters lled with a mixture of 3He and CF4 gas capable of detecting the neutrons liberated by the neutrino-deuteron neutral current reaction in the D2O, and four strings lled with a mixture of 4He and CF4 gas for background measurements. The proportional counter diameter is 5 cm. The total deployed array length was 398 m. The SNO NCD array is the lowest-radioactivity large array of proportional counters ever produced. This article describes the design, construction, deployment, and characterization of the NCD array, discusses the electronics and data acquisition system, and considers event signatures and backgrounds.

Focal-plane detector system for the KATRIN experiment

Abstract The focal-plane detector system for the KArlsruhe TRItium Neutrino (KATRIN) experiment consists of a multi-pixel silicon p-i-n-diode array, custom readout electronics, two superconducting solenoid magnets, an ultra high-vacuum system, a high-vacuum system, calibration and monitoring devices, a scintillating veto, and a custom data-acquisition system. It is designed to detect the low-energy electrons selected by the KATRIN main spectrometer. We describe the system and summarize its performance after its final installation.

Status of and operating experience with the University of Washington superconducting booster linac

The University of Washington superconducting linac uses lead-plated copper quarter-wave resonators for acceleration. These accept a wide range of particle velocities. There are 24 accelerating resonators with β = 0.1 and 12 resonators with β = 0.2, as well as a bunching resonator with β = 0.1 and a rebuncher/debuncher with β = 0.2. These β values are higher than those of other similar machines, reflecting our emphasis on lighter ions. We are able to accelerate ions with masses ranging from 1 through above 60. The linas has been in operation since September 1987. During the early part of this period of operation various systems were completed and debugged, and during the remaining part of the period we have been running fairly routinely while gaining experience and skill in operation. Following a brief description of the accelerator, the operating experience, techniques, and automatic control features will be described in detail.

Dead layer on silicon p–i–n diode charged-particle detectors

Semiconductor detectors in general have a dead layer at their surfaces that is either a result of natural or induced passivation, or is formed during the process of making a contact. Charged particles passing through this region produce ionization that is incompletely collected and recorded, which leads to departures from the ideal in both energy deposition and resolution. The silicon p–i–n diode used in the KATRIN neutrino-mass experiment has such a dead layer. We have constructed a detailed Monte Carlo model for the passage of electrons from vacuum into a silicon detector, and compared the measured energy spectra to the predicted ones for a range of energies from 12 to 20 keV. The comparison provides experimental evidence that a substantial fraction of the ionization produced in the “dead” layer evidently escapes by diffusion, with 46% being collected in the depletion zone and the balance being neutralized at the contact or by bulk recombination. The most elementary model of a thinner dead layer from which no charge is collected is strongly disfavored.

The front end readout of the focal plane detector (FPD) of KATRIN

The design considerations, manufacturing and first tests of the front end readout for the KATRIN Focal plane detector are presented. The main focus is put to the charge-sensitive preamplifiers, which are built as modules with 6 or 7 channels. The prototype results of the charge-sensitive preamplifier-modules gained by charge injection with a test pulser show rise-times of 70 ns, a resulting bandwidths of approx. 5 MHz, a large dynamic input energy ranges from keV up to several MeV and an equivalent noise contribution of approximately 800 eV (FWHM) at room-temperature.

Beam diagnostics for the University of Washington superconducting booster

The beam diagnostic system for the University of Washington superconducting booster provides the operator with a visualization of beam shape, position, intensity, time structure, energy and emittance. Control circuitry, interface structure, display graphics and sensors are described. Measurement of the emittance of the tandem injector and the booster for a variety of beams is in progress. 8 refs., 3 figs.