G. Harper

The STAR time projection chamber: a unique tool for studying high multiplicity events at RHIC

The STAR Time Projection Chamber (TPC) is used to record the collisions at the Relativistic Heavy Ion Collider (RHIC). The TPC is the central element in a suite of detectors that surrounds the interaction vertex. The TPC provides complete coverage around the beam-line, and provides complete tracking for charged particles within ± 1.8 units of pseudo-rapidity of the center-of-mass frame. Charged particles with momenta greater than

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.

STAR TPC at RHIC

Design information, construction methods and testing results are given for the STAR TPC which will be installed at the BNL RHIC collider.

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.

The laser system for the STAR time projection chamber

Abstract The Time Projection Chamber (TPC) is the core tracking detector for the STAR experiment at RHIC. To determine spatial distortions, calibrate and monitor the TPC, a laser calibration system has been built. We developed a novel design to produce ∼500 thin laser beams simulating straight particle tracks in the TPC volume. The new approach is significantly simpler than the traditional ones, and provides a higher TPC coverage at a reduced cost. During RHIC 2000 and 2001 runs the laser system was used to monitor the TPC performance and measure drift velocity with ∼0.02% accuracy. Additional runs were recorded with and without magnetic field to check E×B corrections.

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.

Dead layer measurements for KATRIN prototype PIN diode array

Dead layer measurements for a prototype PIN diode array for the KATRIN (KArlsruhe TRItium Neutrino) experiment are presented. KATRIN is a direct neutrino mass measurement of tritium beta decay near the electron endpoint energy of 18.6 keV. A neutrino mass sensitivity goal for KATRIN is m(ve) < 0.2 eV. The methods used to determine the dead layer include the standard angle method, commonly found in texts, and the newly developed energy method. An average dead layer across the entire array of 119 plusmn 3 nm and 109 plusmn 3 nm, was found respectively for the two methods.

Hardware controls for the STAR experiment at RHIC

A hardware controls system has been implemented for the STAR experiment at RHIC. Approximately 10000 parameters governing experiment operation are currently controlled and monitored. The system is based on the Experimental Physics and Industrial Control System (EPICS). The architecture of STAR hardware controls are presented as well as the results of operation of the integrated baseline system. Novel features of the system include a specialized field bus (High-level Data Link Control-HDLC), new EPICS record support, control DEVice (CDEV) interfaces to accelerator and magnet control systems, and C++ based communication between STAR online and hardware controls and their associated databases.

2 1 + to 3 1 + γ width in Na 22 and second class currents

A previous measurement of the