REAL-TIME X-RAY BEAM POSITION MONITOR FOR SYNCHROTRON BEAMLINES

The RIGI is a 4-quadrant beam position monitor suited for hard X-ray synchrotron beamlines. It is ultra-high-vacuum (UHV) compatible, can remain continuously in the X-ray beam and allows monitoring the position of the X-ray beam in real time with a sub-micron precision. The RIGI is available with two different active areas matching the beam cross-section of most beamlines. It is very simple to install and to operate.

KEY ADVANTAGES

  • Very low X-ray absorption and phase contrast allowing for several devices in the beamline  
  • Submicron resolution 
  • Excellent temporal response
  • Outstanding thermo-mechanical properties and radiation hardness
  • Very compact: thickness 1 mm without cover
  • UHV compatible 

APPLICATIONS

  • Online feedback 
  • Full positional and angular beam characterization
  • Automatic beamline alignment
  • beam intensity monitoring
  • Detection of beamline and source instabilities
  • Pink beam monitoring

Principle

The RIGI is based on a very thin CVD diamond membrane and is operated like a solid-state ion chamber. Typically a bias voltage of 10 kV/cm is applied. The resulting dark current is very low thanks to the high resistivity of diamond. The absorption of the X-ray beam generates free charge carriers in the diamond layer and hence a photocurrent is induced. With an external picoampere meter, this photocurrent can be measured for each pad. The difference of photocurrent between pads over the total current gives the signal, which can be calibrated to provide positional information.

Fig. 1: Transmission of 1, 2 and 5 RIGI X-ray beam position monitors as a function of photon energy.