Auxiliary Equipment and Techniques
At the Argonne National Laboratory (ANL) Physics Division target facility we have employed the rolling technique to produce a wide variety of foil targets covering isotopes over most of the periodic chart. Another area where the rolling method is used is for the preparation of numerous filters, degrader foils and various windows needed for detectors and gas cell targets. The apparatus employed for mechanical rolling of metal foils is a Durston Type SE/EX electric rolling mill obtained from Frei & Borel. It consists of two hardened and polished rolls of width 120 mm working size and a diameter of 60 mm.
New rolling mill acquired in March 1997.
Previous rolling mill, now relocated to the Radioactive
J.P. Greene and G.E. Thomas, Physics Div., Argonne National Lab. PHY-8557-HI-96 (1997).
Recent research has shown electrodeposition a useful process in the production of certain targets (for example Cd and Zn). We have found that the method of electrolytic reduction is quite economical for extracting isotopic metals to be used later for rolling or evaporation. A photograph is given below showing the experimental set-up in detail.
Experimental set-up for electro-deposition.
INTDS Newsletter. 26(2), 11-17, 1999.
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. 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.
Alpha particle energy loss target thickness system
Close-up of the alpha particle energy loss target
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.
Larger Alpha particle energy loss target thickness system.
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 plastic 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.
Plastic desiccators for the storage of materials.
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 Reactions.
Nuclear Instruments and Methods in Physics Research A 613 (2010) 462-464