[continues from 4.6.2]

4.7 Detector resolution

The detector resolution has been computed from monochromatic line spectra taken at the Panter facility. The typical line has a Gaussian shape plus a low energy tail.

4.7.1 Gaussian component

The Gaussian component for a given input energy is represented by a gaussian (of arbitrary normalization D1) centered at the PI channel (D2) given by the gain relation broadened with a given sigma (D3).

		Gi(Ej) = D1 exp(-0.5 [(PI-D2)/D3]2)

where PI indicates the i-th output channel.

As customary for proportional counters, instead of the sigma one gives the FWHM as DeltaE/E %. The energy dependency is proportional to E-1/2 and therefore a single parameter FWHM6 (the FWHM at 6 keV) is sufficient to describe it:

Such values for the three MECS units are all stored in a single file resolution.coeff.

The sigma at any energy can therefore be easily computed as :

                sigma = D3 = 0.01 FWHM6 61/2 E1/2 / 2.355

Fig. 4.7.1-I : MECS spectral resolution
We report also, as example, experimental measurements for M1.

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