Beam Stoppers Research Articles

Tests and Description of Beam Containment Devices and Instrumentation - A New Dimension in Safety Problems

The destructive capability of the beam power of some accelerators was dramatically demonstrated in a series of tests at SLAC using an 18 GeV e- beam at average powers ranging from 165 to 880 kW. The purpose of the experiments was to examine a series of devices which simulated beam stoppers, protection collimators and burnthrough monitors as presently applied at SLAC. Specific attention was given to the recording of burnthrough times, temperature behavior, and to the analysis of failure modes. A summary of the test data is presented. The design of an extensive electronic system to prevent damage to mechanical devices and to detect onset of destruction is discussed. Various sensors are connected to integrating and peak reading circuits to form power, beam verification and errant beam monitors. Burnthrough monitors shut down the accelerator if damage occurs to critical items. New features such as self-checking, protected wiring and rapid on-line calibration are described.

A Precision Actuator and Shaft Encoder for a High Radiation Environment and Other Beam Component Developments at SLAC

A precision actuator and shaft encoder combination for remote handling in a high radiation and corrosive environment is described. The package allows accurate positioning of beam transport components in areas where liquid lubrication is not possible. The use of hexagonal lattice metals prevents galling or seizing of the rolling surfaces. The actuator translates rotary motion and torque supplied by a commercial radiation-resistant stepping motor into linear motion and force. Two actuators are in operation with a 7.5 cm output travel. Reproducibility is to ±1 step or 0.0015 cm. The shaft encoder resolves the turns of the motor in 1024 increments with cams and microswitches. The estimated dose rate of 1012 to 1013 ergs/g/yr in the vicinity of a SLAC high-power slit should present no problems. The second part of the paper describes a new quick-disconnect injected indium vacuum seal. Indium is extruded into a gasket groove of a flange through tapped holes by means of bolts. Finally, a blowout fuse employed in the beam stoppers of the SLAC personnel protection system is described. The fuse responds to thermal radiation from the surface of a beam stopper by melting a low-temperature eutectic diaphragm thus letting the vacuum system up to air.

Design of new diagnostic x-ray departments--protection aspects.

The requirements of radiation protection for X-ray diagnostic departments should be included in the considerations of siting and layout of the whole department. The layout of the individual X-ray rooms and the material from which they are constructed have a considerable bearing upon the additional shielding which is necessary, but attention to detail can improve ease of working and reduce capital outlay while still maintaining a very high standard of protection. The incorporation of “beam stoppers” into X-ray equipment could considerably reduce shielding problems.