Silicon detector response to heavy ions at energies of 1-2 MeV/amu

The response of silicon detectors has been measured for He, O, S, Cl, Br, Ag and Pb ions in the energy range 1-2 MeV/amu. Following deliberate, long exposures of the detector, a transient effect was observed for 140 MeV Br ions, in which the pulse height decreased with increasing ion dose and then partially recovered within an hour of the final exposure. Using brief, consecutive exposures, the effective energy for creating a detectable electron-hole pair was determined using the pulse height difference method. The energy deposited by ions in the 'dead-layer' at the detector surface and energy loss via non-ionizing events was taken into account. For ions with atomic numbers 2 ≤ Z ≤ 17 and energies above the Bragg peak, the effective energy was found to decrease linearly with increasing electronic stopping power at first, and then to level off at 3.52 eV/electron-hole pair. For intermediate mass ions (17 < Z ≲ 40), at energies close to the Bragg peak, increases slightly (∼2%) with increasing stopping power. For the heaviest ions studied (Z ≳ 40), whose energies are below the Bragg peak of the stopping power curve, increases strongly (∼10-20%), even though the electronic stopping power is approximately constant.