Radiobiology Research Facility
Complementing the NASA Radiations Effects Facility (NSRL) at BNL, we have recently developed a lower ion energy radiobiology research facility at the Tandem 1). Low energies may be of particular interest since the high energy ions lose energy when traversing spacecraft materials and produce the maximum damage just before coming to rest in the astronauts’ bodies. Thus, energies lower than most present in the primary cosmic ray spectrum are appropriate to cover the range of maximum LET (the Bragg peak ) but, due to their short ranges, they are only useful to perform studies with thin samples such as cell cultures. Figure 1 illustrates the very large range of LET values and respective penetration depths in water (or tissue) for iron beams from 10 keV per nucleon to 1 GeV per nucleon.
Figure 1: LET values and ranges of iron ions in water for energies from 10 keV per nucleon to 1 GeV per nucleon. The energies available from the BNL Booster and Tandem accelerators are indicated.
Figure 2 shows the new radiobiology irradiation enclosure to the right, the large SEUTF chamber in the middle and the dosimetry chamber to the left. The ion beams go through the SEUTF chamber before entering the irradiation enclosure. A very thin but strong vacuum window is necessary to allow the ions to exit the vacuum without losing too much energy. The material chosen is a Co, Cr, Ni and Fe based alloy called HAVAR that is available in thicknesses down to 100 micro inches or 2.54 micro meters.
Figure 2: The radiobiology irradiation enclosure is shown at the right of the picture, the Single Event Upset Test Facility (SEUTF) chamber in the middle and the dosimetry chamber used for both at the left.
Figure 3 shows the linear translation stage with insertable dish holder and two installed culture dishes. The stage allows samples to be repeatedly scanned across the ion beam. The stage is shown in its leftmost, parked position.
Figure 3: The linear translation stage with insertable dish holder and two installed culture dishes
Below is a movie showing the cell culture dishes moving at constant speed across the ion beam.
Complementing this irradiation station there is a nearby hood, an incubator and work benches (figure 4) appropriate for handling and storing cell culture samples before and after irradiation.
Figure 4: Hood, refrigerator and incubator for storage of cell culture samples.
Typical ions available for radiobiology research are listed in Table 1
| Ion | Z | Energy from accelerator | Energy at Sample | LET In Water | Range In Water | |
|---|---|---|---|---|---|---|
| (MeV/u) | (MeV/u) | (KeV/μμ) | (μμ) | (mm) | ||
| p | 1 | 28.8 | 28.8 | 2 | 8050 | 8.05 |
| Li | 3 | 9.6 | 9.6 | 50 | 657 | 0.66 |
| B | 5 | 7.9 | 7.8 | 147 | 348 | 0.35 |
| C | 6 | 8.3 | 8.2 | 208 | 282 | 0.28 |
| O | 8 | 7.1 | 6.9 | 400 | 179 | 0.18 |
| Si | 14 | 5.8 | 5.3 | 1210 | 91 | 0.09 |
| Fe | 26 | 4.6 | 3.6 | 3730 | 55 | 0.06 |
| Ge | 32 | 3.7 | 2.6 | 5400 | 44 | 0.04 |
| Ag | 47 | 2.9 | 1.7 | 8250 | 35 | 0.04 |
| Au | 79 | 1.7 | 0.8 | 11400 | 30 | 0.03 |
Table 1 Maximum energies and corresponding LET values and ranges in water for some of the heavy ions that are available for radiobiological studies at the BNL Tandem. Lower energies can also be selected
The linear energy transfer (LET) values as function of energy for some of the typical ions listed in Table 1 are shown in Fig. 5.
Figure 5: LET values in water as function of energy for four of the ion beams available at the BNL Tandem. The available energies are indicated in red.
Figure 6 shows energy and LET values in water (or tissue) as function of depth for three of these ion beams.
Figure 6: Energy and LET values in water (or tissue) as function depth for three beams available at the BNL Tandem accelerator facility.
This radiobiology research facility at the Tandem extends the ion energy range available for radiobiology experiments at BNL. Full advantage is taken of the existing infrastructure including excellent dosimetry, the established user program, and the support functions developed by the Medical and Biology Departments for NSRL. The close proximity of this facility to the NSRL and to the BNL Biology and Medical Departments has proven convenient for researchers.
Scheduling time at this facility is easy. The schedule is flexible and ion beams are available all year long.
Reference: 1) http:/three. usra.edu/articles/FinalThieberger032912.pdf
