Converting LET to Energy of Particle

Once the chips are calibrated, it may be possible to measure the energy deposited in the detector in real energy units. However, what is important to bare in mind is that energy deposited in the detector surface is not always directly proportional to the energy of the incident particle: they can only be said to be equal if the particle is stopped within the surface.

We have not yet researched this issue in-depth for the sort of particles likely to be detected in RAY: however, there is software available for converting the Linear Energy Transfer (LET) of ions to the energy of the particle. The LET is rate of energy transfer with respect to distance travelled by the particle in the detector surface - the energy deposit of the track over the track length (once charge sharing is adjusted for).

Other particles should behave in a similar manner to the ions, insofar as there is a peak LET at some definite non-infinite energy value. This means that a single LET value can indicate at two different particle energies.

LET_energy_light_ions.jpg

Fig 1: A graph showing the LET of light ions in silicon at various energies. Data is from The Stopping Range of Ions in Matter (SRIM) software.

The same essential principles should apply to higher-energy beta tracks. The non-straight nature of their tracks would make calculating track length, needed for LET, difficult, though: further investigation is needed. Alpha particles can mostly be assumed to have deposited all their energy in the silicon at the energies dealt with in RAY.

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