Abstract
Ground arrays for UHECR shower detection based on traditional counters, water Cerenkov tanks or scintillator modules, are unavoidably limited by the saturation suffered by the counters nearest to the shower axis. Reducing to a negligible level the amount of events recorded with saturated counters should be mandatory in a future UHECR ground array. The use of the signals extracted from the internal dynodes of the used photomultipliers can offer an elegant and inexpensive way to increase the dynamic range of such detectors. The viability of this technique has been explored studying in laboratory the performances of a sample of 3 Hamamatsu R5912-MOD photomultipliers. Exploiting the signal from the fifth dynode, a linear response up to an equivalent anodic peak current larger than 1A (at gain G = 2 ⋅ 10 5 ) has been measured for all the studied PMTs. The feasibility of this technique in the frame of a new ground array for UHECR studies should be verified with a larger sample of photomultipliers.
Highlights
One of the main limitations suffered by EAS arrays aiming at sampling the number of particles at ground level is the saturation of the counters close to the shower core, due to the high particle density hitting the detectors
The possibility of extending the linear dynamic range of a PMT has been investigated by using the dynode output signals
The linearity range of the inner dynodes of three Hamamatsu R5912-MOD PMT has been measured in laboratory
Summary
One of the main limitations suffered by EAS arrays (water Cherenkov or scintillation detectors) aiming at sampling the number of particles at ground level is the saturation of the counters close to the shower core, due to the high particle density hitting the detectors. The present limit of photomultipliers like those operating at the Pierre Auger Observatory (Photonis XP1805) is 200 nA [1], at the nominal gain G = 2 · 105. The use of these PMTs in the highest energy range implies an extension of the dynamic range by a factor ∼60. 5th dynode, the available linear range was at least a factor of 20 larger than the present Auger water Cherenkov detectors one. The signals of all the dynodes from the 8th (D8) to the 4th (D4) have been extracted, and their response has been compared to the anodic one assumed as reference signal
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