| Zhongwei Du wrote: |
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Hello.
We are designing a waveform sampling board for Si strip array detector ,whose rise time is less than 10 ns, which makes we doubt whether the DRS4 can do more accurate than traditional charge integral circuit for charge measuring.
So we need to know what sort of detectors for physical experiment the DRS4 has been used in?
Can you give me some information? For example, Si strip array detector or CsI scintillator r ball detector ? PMT or APD ?
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DRS4 is used for PMTs and APDs. The minimal rise/fall time which can be recorded with the DRS4 on the evaluation boards is about 0.8ns (see elog:84). Concerning charge measurement, it depends on your integration time. If your signal is for example 20ns and you sample with 5 GSPS, you get actually 100 samples. You digitize with 12 bits, but the S/N ratio is more like 11.5 bits. But since you have 100 samples, the accuracy of the measurement scales with sqrt(100)=10. So you have more like 11.5+3 bits = 14-15 bits, or a SNR of 20'000. Now your signal usually does not have an amplitude of 1V, will be more like 100mV or so, in which case your SNR goes to 2000. But this still gives you a resolution of 1/2000 = 0.5 per mille.
We did tests with a Ge detector for spectroscopy applications, where we used a shaping time of 2 micro seconds, both with traditional electronics and the DRS4, integrating the signal over 2 micro seconds. Both gave a resolution of about 0.4%, indicating that the resolution was not limited by the DRS but by the detector.
Best regards,
Stefan |