Prototype tests of two controlled geometry drift chambers

The HERMES Back Drift Chambers

The tracking system of the HERMES spectrometer behind the bending magnet consists of two pairs of large planar 6-plane drift chambers. The design and performance of these chambers is described. This description comprises details on the mechanical and electronical design, information about the gas mixture used and its properties, results on alignment, calibration, resolution, and e ciencies, and...

Drift and Proportional Tracking Chambers

The Drift Chambers Of The Nomad Experiment

We present a detailed description of the drift chambers used as an active target and a tracking device in the NOMAD experiment at CERN. The main characteristics of these chambers are a large area (3 × 3 m), a self supporting structure made of light composite materials and a low cost. A spatial resolution of 150 μm has been achieved with a single hit efficiency of 97% . 1 on leave from the Labor...

Ultraviolet Laser Calibration of Drift Chambers

We demonstrate the use of a focused ultraviolet laser as a track calibration source in drift chambers, and specifically in a small time projection chamber (TPC). Drift chambers such as TPCs reconstruct the trajectories of charged particles by amplifying and collecting electrons produced by ionization of gas atoms with which the target particle collides. The ultraviolet laser induces a two-photo...

The Geometry of Two-stage Tests

Sample size calculations require specification of the treatment effect, but what if this is not known? Two-stage tests use the first stage to estimate the treatment effect and modify the sample size accordingly. The purpose of this paper is to unify the theory of two-stage testing based on treatment effect. The conditional error function approach of Proschan and Hunsberger (1995) is shown to be...