The Proton Irradiation Facility (PIF) makes use of two beam lines at TRIUMF for low intensity radiation damage studies of electronics, detector components and other materials. Low energies, variable from as low as 15 MeV up to 120 MeV are available from the beam line 2C, which is also used on a regular basis for proton treatments of ocular melanoma. Higher energies, from 120 MeV up to 500 MeV are available from a second beam line 1B which transports proton beams into the same experimental area. Table 1 gives a summary of the beam sizes and intensities that are available on PIF. The unique feature of the TRIUMF cyclotron is that it is capable of extracting simultaneously several beams of different energies and intensities. This is achieved by accelerating H- ions and using a stripping foil or wire, located at the correct radius in the cyclotron, to extract protons of the desired energy. The intensity is determined by the area of the stripping foil intercepting the beam and is adjusted with the height and shape of the foil.
The irradiation facility was designed primarily for single-event effect studies and characterization of electronics components for the space environment. The spectrum of trapped protons in earth orbits peaks in the 10-100 MeV energy region (depending on the amount of intervening absorber) and drops by about an order of magnitude at 500 MeV. This makes the TRIUMF variable energy capability up to 500 MeV ideal for studies of space effects. Biological studies such as cell irradiations to measure RBE of protons are also being carried out in conjunction with the Proton Therapy Facility.
Figure 1 shows the layout of the PIF experimental area. Beam line 1B is used to transport low intensity (~ few nA) protons with energies from 180-500 MeV into the area. The front section contains the beam primary collimator and scatterer and has a test location for higher flux testing. The back section contains the beam diagnostic equipment, the X-Y table for device positioning and the beam defining collimator. Nearby is the lower energy beam line 2C (65-120 MeV) which provides protons to the Proton Therapy Facility and is easily configured for PIF applications. Energies lower than the lowest extracted energy can be obtained by putting material in the way of the beam to degrade the energy. The energy spread of the proton beam after the absorber will be greater than the 1-2 MeV FWHM of the incident beam due to straggling and this can be calculated for the specific situation.
Low intensity neutron beams can also be obtained by stopping the protons in a full energy blocker and setting up downstream of the blocker. The neutron spectrum is not monoenergetic but has an energy spectrum up to the maximum proton energy.
The extraction system for BL1B is shared with BL1A and is normally available
for PIF use only when low intensity beam is circulating in the cyclotron.
Proton therapy uses a modulated 74 MeV beam and is scheduled
for operation one week per month. The lower energies are therefore available
more frequently.