An overview over RERS2 is given. A detailed description, including many technical details such as required cable lengths, collimator sizes, area layout etc., can be found in the user's guide. Construction of the RERS2 beamline was completed in September 2003. Fig.1 shows the end of the RERS2 beamline. The first 205 MeV beam was tuned down the beamline in late September. Energy degraded, momentum analyzed beams are now available. The first energy degraded beam was delivered in December 2003. RERS2 has the following features:
- 45 - 200 MeV proton beam, momentum analyzed
- 2 to 30 cm diameter beamspot
- fluxes 102 and 1011 p/s cm2
- uniformity: <30% variation over area
- exposure durations 5s - several hours
- absolute dosimetry better than 10%
RERS2 is the preferred beamline if energies lower than 200 MeV with a narrow beam energy spread are desired. A Beryllium degrader far upstream of the device under test is followed by magnetic momentum analysis. The remotely controlled degrader wheel is shown in Fig. 2. As a result, the beam energy spread is small at all energies. The flux depends strongly on energy, because the momentum selection system only transmits that portion of the beam which has the desired energy downstream of the beryllium degrader. Obviously, there is a trade-off of narrow beam energy spread vs intensity. The "maximum flux" button may be used to calculate the maximum flux as a function of energy. The method of choice to degrade the beam energy depends on the application and whether high flux or small energy spread is the prime concern.
The four existing Beryllium degraders are 3.05", 5.06", 6.05" and 6.55" thick, corresponding to 149.0, 102.1, 71.9 and 52.0 MeV after the degrader.
The device under test (DUT) is in air and mounted on a x,y,z adjustable table, which is remotely positionable in the two dimensions, x and y, perpendicular to the beam direction. Alignment of the DUT is conveniently accomplished with a laser which points in the beam direction.
The usual beam spot size is 7cm in diameter. The irradiated area may be restricted by use of collimators. Larger or smaller beam spot sizes (2 - 30 cm diameter) are also available.
For fluxes between 105 and 1011 p/s cm2 a calibrated secondary electron monitor (SEM) is used for dosimetry. For fluxes between 102 and 106 p/s cm2 a scintillator is used. The two devices are cross-calibrated between 105 and 106 p/s cm2.
Figure 1: View of the end of the RERS2 beamline.
Figure 2: Degrader wheel for RERS2. At present, four Beryllium degraders are mounted. There is room for a fifth degrader. One position remains empty for 200 MeV beam.
For additional information on RERP or to schedule an experiment
please contact Barbara von Przewoski:
(812) 855-2913
(812) 855-6645
bvonprze(at)indiana.edu
RERP, Indiana University Cyclotron Facility
2401 N Milo B. Sampson Lane
Bloomington, IN 47408
