Front ends of synchrotron radiation beamlines on Indus-1 

Adu Verma and R V Nandedkar 

Synchrotron Utilization Division

1. Introduction:

On Indus-1, number of synchrotron radiation beamlines are already installed. In order to achieve a long beam lifetime, the pressure in the storage ring and the beamlines must be maintained at Ultra High Vacuum (UHV)  (<1´10^-9 mbar). The beamlines are operated by number of research personnel and there are chances of instantaneous vacuum failure or gas leakage at down stream of any beamline. Such a failure would result in fatal damage to the storage ring, causing costly evacuation procedure and shutdown time. In such a circumstances “Front Ends” are required for synchrotron radiation beamlines which protect the ultra high vacuum of storage ring in sudden vacuum failure / gas leakage in the down stream of any beamline.

2. System Description:

On Indus-1, front ends have been developed and installed for photoelectron spectroscopy beamline, reflectometry beamline, and photophysics beamline respectively. The design and commissioning of these three front ends and their supporting stands is a challenging work due to metallic trenches all around Indus-1 ring and very short space available between Indus-1 beamline port and shielding wall. The front end of beamline consists mainly of a UHV vessel, fast closing shutter, UHV gate valve, sensor and a controller. The schematic diagram of the front end is given below. As per this diagram the fast closing shutter has been assembled at the front of the beamline. A slow closing UHV gate valve backs up this fast closing shutter. The shutter and valve are controlled by a electronic controller. The controller has a cold cathode gauge as a vacuum detector assembled at downstream of the beamline .The pressure in the beamline is measured with the ion current signal of the vacuum detector, which is transmitted to the controller. The distance between the detector and fast closing shutter is approximately 10 meters and pressure ~ 1´10^-3 mbar liter ¤  seconds of trigging point has been set on the controller.

After commissioning of the front end on reflectometry beamline on Indus-1, a performance test has been carried out, during the performance test we have generated a leak of 1´10^-3 mbar lit/seconds at downstream of beamline and found that the pressure in the storage ring rises from 1´10^-9 mbar to 1´10^-8 mbar which is pump out and initial vacuum 1´10^-9 mbar maintained within short period.