Klystron Department

Compton X-Ray Laboratory

In collaboration with U.C. Davis, a program is underway at SLAC to develop a source for generating monoenergetic, tuneable X-rays in the multi-keV domain (20-85 keV). The goal is to demonstrate a proof-of –principle device useful in the diagnosis and treatment of cancer.

The X-rays are generated via the Compton Effect in a (nearly) head-on collision of a multi-MeV electron beam with a high power, infrared laser beam (1-2 TW). The backscattered photons will be in the KeV energy regime, determined by the electron beam energy. Since the requirement of monoenergetic X-rays depends critically on the electron beam energy-uniformity and quality, a laser driven RF gun is used to generate sub-picosecond electron bunches. Further acceleration is accomplished through the use of a high gradient X-band accelerator structure developed for the Next Linear Collider (NLC).

The key beamline components in this experiment are the RF gun, emittance compensating solenoid, mirror chamber, accelerator, magnetic focusing elements diagnostic chamber, an interaction chamber where the photon and electron beams collide and a final observation chamber. Each of the chambers is equipped with a removable Ce:YAG scintillator to permit beam optimization along the beamline. In addition, metallized pellicles are installed in some of the chambers for OTR observation and slits for emittance measurements. A schematic of the setup is shown below. The RF setup and the high power laser system are located in a radiation shielded enclosure with RF power supplied externally by two X-band 60 MW NLC klystrons. Table 1 lists the overall capabilities and design requirements of the complete system.
 

 

Table 1. Operating parameters

Klystrons: Accelerator Structure:
1. Peak RF Power-60 MW 1.  RF Power 42 MW Ž 53 MV/m
2. Peak available pulse width-1.5 µs. 2. Pulse repetition rate 60 pps
3. Max. Pulse repetition rate- 60 Hz 3. Pulse width:  RF 250 ns., beam <1 ps.
RF Gun: High Power Laser:
1. RF Power 16 MW Ž 200 MV/m 1. Pulse repetition rate 10 Hz
2. Max. Pulse repetition rate 60 Hz 2. Pulse width at Interaction chamber: 50 fs.
3. RF pulse width 200-250 ns. 3. Peak Energy 100 mJ at 800 nm.
4. Charge/pulse-0.5 nC 4. UV energy 120 µJ
  5. UV laser radius at cathode-0.5 mm
6. UV Pulse width-100 fs.

 
 

 

Last Page Update:
Wednesday June 01, 2005