[Solid_ec] calculation

[Xiaochao Zheng]

Two more points:

1) R11102 is a 10-stage PMT, so maybe the power "b" is not exactly the number of stages.

2) The Hamamatsu datasheet for R11102:
https://www.hamamatsu.com/resources/pdf/etd/R11102_-01_TPMH1324E.pdf

shows that the gain approximately doubles for every 100 V increase in HV, on the double-log scale. This is consistent with what Chendi got.

So again, I think the gain results are good, and the problem is elsewhere.

Xiaochao

----- Original Message -----
> From: "Xiaochao Zheng" <xiaochao at jlab.org>
> To: "cunfeng feng" <cunfeng.feng at cern.ch>
> Cc: "申忱迪" <15600915869 at 163.com>, "solid ec" <solid_ec at jlab.org>
> Sent: Thursday, September 7, 2017 11:23:55 PM
> Subject: Re: [Solid_ec] calculation

> Hi Cunfeng:

> There is a slight difference here: When the curve is linear on the double-log
> scale, one could have:
> gain = a * (HV)^b, where a and b are constants. Looking at Chendi's data (see
> the spreadsheet file on the minutes), the value of b seems to be about 8.1,
> which is likely to be the number of stages for this PMT. In this case, the
> increase in the gain per dynode is linear with HV, and the total gain is HV
> raised to the power of number of stages, and thus Chendi's results are
> reasonable and is consistent with what we expect.

> At the meeting JP said what CHendi showed agrees with JP's experience. He said
> for the Hall A HRS detectors, when the HV is increased by fixed amount (such as
> 100V each time), the gain increase by a fixed scaling factor (for example,
> doubles every 100V). THis can be either explained using the single log scale
> function, or a power function as above.

> So I think the problem may be elsewhere:
> 1) Can the PMT anode current saturate?
> 2) Can the attenuator that Chendi used behave non-linearly?
> 3) If we do a HV scan for the SDU3 module, is it possible to show the same
> (weird) behavior? Can the SDU group do such a scan to prove the method to be
> valid? (That we should get a fixed Npe for different HV values)?

> Thanks,

> Xiaochao

>> From: "cunfeng feng" <cunfeng.feng at cern.ch>
>> To: "申忱迪" <15600915869 at 163.com>, "Xiaochao Zheng" <xiaochao at jlab.org>, "solid
>> ec" <solid_ec at jlab.org>
>> Sent: Thursday, September 7, 2017 10:56:18 PM
>> Subject: Re: [Solid_ec] calculation

>> Chendi,

>> I agree with Xiaochao that the Gain-V relation is linearity under double-log
>> axis as shown on the PMT specification sheet, not single-log axis. You should
>> contact with the PMT company to explain why the Gain-V results is not linearity
>> under double-log axis.

>> Your PMT Gain raises much more, it should be the reason the NPE decrease.

>> Cunfeng

>> On 2017/9/7 22:26, 申忱迪 wrote:

>>> hello

>>> here is my calculation.

>>> best regards

>>> --
>>> 申忱迪 Chen-di Shen
>>> Department of Engineering Physics, Tsinghua University
>>> 418, Liuqing Building, THU, Haidian District, Beijing, China, 100084
>>> Tel：86- 15600915869 & 86-18101259887
>>> email: shenchendi404 at 163.com

>>> _______________________________________________
>>> Solid_ec mailing list Solid_ec at jlab.org
>>> https://mailman.jlab.org/mailman/listinfo/solid_ec

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