Auxiliary Equipment

Auxiliary equipment used for target development includes an alpha particle counting chamber, inert atmosphere glove box, laminar flow clean bench, pellet press,a reduction furnace,and a variety of precision balances.

This glove box is utilized for the production of air-sensitive targets.

Clean hood used for static-sensitive targets among others.

Balances used for weighing of chemical materials as well as target foils.

Tube Furnace for Hydrogen Reductions

Alpha Particle Counting System

As a check of the deposited film thickness as measured using a quartz oscillator, an alternate means of measuring target thickness is desirable. A set-up was constructed within the target laboratory to determine target thickness using the energy loss of alpha particles from a 249Cf source. An ADC data-acquisition board and software were purchased for our laboratory computer for this purpose. Target thickness is obtained from the measured energy loss, determined specific to the target material, and calculated using Ziegler's formulas.

Alpha particle energy loss target thickness system with laboratory computer.

The foil to be measured is placed within a mechanically-pumped vacuum chamber between the 249Cf source and a silicon surface-barrier detector. Small apertures are positioned above and below the target in order to collimate the alpha particles. A close-up photograph of a target to be measured is shown below.

 

The alpha counting system presently used was constructed to measure target foils, which, including the target frame, are usually no larger than 2.5 cm by 2.5 cm. The small vacuum chamber cannot accommodate the large degrader foils, employed to slow down recoiling nuclei, metallized gas detector windows of various sizes and large area targets used in COULEX experiments. For this reason, a larger chamber, needed for alpha particle counting, was constructed to accept and measure these large area foils.

 

 

 

 

Target Storage Facility

A Varian V-200 turbo-pumped target storage facility is in operation for maintaining, under high vacuum, those targets, which can readily oxidize in air. This system utilizes computer-controlled circuitry to prevent targets from exposure to atmosphere during power interruptions. Within the vacuum chamber there exists a carousel capable of storing 100 targets. Loading and unloading targets is accomplished using a vacuum interlock, which can connect directly to the ATLAS experimental apparatus.

Computer Controlled High-Vacuum Target Storage System

A second system of target storage employs a bank of vacuum desiccators connected to a mechanically pumped manifold for use by individual experimenters. This vacuum system includes an emergency shut-off valve, which prevents venting of the desiccators to atmosphere during power interruptions. Duplicates of both these systems have been constructed and are currently installed at ATLAS for the storage of air-sensitive targets which have been activated by the beam

Target Storage Desiccators connected to a mechanically pumped vacuum manifold.

An additional system consisting of two large glass desiccators evacuated using a small turbo-pump system is in operation for material storage. This separates material from the target storage, hence eliminating repeated exposure when transferring and retrieving targets.