Speaker
Stanislav Potashev
(Inst. of Nucl. Research, Moscow)
Description
A system of three ion-chambers with low threshold energy, giving new
possibilities in proton beam monitoring and analyzing, is considered. The
system includes a new double-gap chamber with the gap of 1 mm, with
polyimid films of 3 μm thickness and with the sensitive area 113 cm 2 and
two double-gap ionchambers, each with the gap of 2 mm. Ionization losses
in each of six sensitive air gaps, as well as losses for 64 strips, are measured
in coincidence for every accelerator spill. Total amount of non-sensitive
material crossed by the beam is only 3.9 mg/cm 2. Protons at Bragg-peak
energy and below are capable to penetrate the anode which separates two
neighbour gaps and peculiar behavior of loss correlations can be observed.
This behavior can be explained by alternative trends of energy-loss
dependence below and above Bragg peak. Recombination contribution is
estimated as only few percents at 1 nA/cm 2. An essential contribution to
the dose from protons at about 1 MeV and below was demonstrated both by
calculations and experimental data. Selected contributions of fast and slow
protons and δ-electrons to the energy loss can be extracted from the data.
The system demonstrated a stable operation after a proton irradiation of 5
Mrad.
Primary author
Stanislav Potashev
(Inst. of Nucl. Research, Moscow)
