[Solid_ec] calculation

[Cunfeng Feng]

simple calculate:

1.1^8.1=2.16, Gain at 1100V should be 3.1*2.16=6.7>6.5(chendi 
list)(3.1is the gain at 1000V)

1500V : 1.5^8.1=26.7, =>G=3.1*26.7=82.7<102(chendi's)

So the relation not normally as G=a*V^b.



On 2017/9/8 11:23, Xiaochao Zheng wrote:
> 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 <mailto:shenchendi404 at qq.com>/
>
>
>
>
>
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>

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