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Investigation of Coating on 5" PMTs

Sep. 2000

Type: Photonics XP4572/B/D1 (for A2)   :

Eric got improvement of 14% for 5kÅ coating, and 15% for 7.5kÅ coating.
 

Serial No.
  Coatinga  File(Date) HV Rate(Hz) Apedb A1b Aavc Ntotd A1/Aav N>d µe sigma(µ)e Comments
60036 (TN15) No
As reference		 L5001(08/29) 1900 3k 41.0 167.2 180.8 73559 0.92 16694 0.257 0.002
  • A1 changed
L5002(08/29) 1900 3k 40.8 115.1 123.3 31895 0.93  7366 0.263 0.002
L5010(09/02) 1900 3k 41.0 147.6 159.3 51325 0.93  11704 0.259 0.002
60011 (TN11) 10kÅ PTPH L5004(08/30) 1900 2k 40.9 141.2 152.9 30419 0.92   7600 0.287 0.002
  • Difference of 13% 
 wiped L5008(09/01) 1900 2k 40.9 141.3 151.5 35250 0.93   7891 0.253 0.002
60006 (TN14) 75% PTPH->15kÅ L5005(08/31) 1980 2k 40.9 133.2 144.0 60903 0.93 16127 0.308 0.002
  • Difference of 16%
  • A1 Changed
wiped L5009(09/02) 1980 2k 40.9 110.1 117.2 58723 0.94 13650 0.265 0.002
60029 (TN09) 50% PTPH->10kÅf L5007(09/01) 1680 2k 41.0 145.7 156.3 55099 0.93 13930 0.291 0.002
  • Difference of 14%
  • A1 changed
wiped L5011(09/03) 1680 2k 40.9 131.9 141.6 56848 0.93 12787 0.255 0.002

==================================
Thickness(kÅ):       5      7.5        10             15
Improvement:      14% 15%    13%,14%    16%
by                         Eric  Eric        L.Y.         L.Y.
==================================

Type: Burle (for Gas Cherenkov and A1)

Eric got improvement of 10% for 10kÅ coating, and 17% for 5kÅ coating.
Don't take too serious about my results below . I may make some silly mistakes.
 

Serial No.
  Coatinga  File(Date) HV Rate(Hz) Apedb A1b Aavc Ntotd N>d µe sigma(µ)e Comments
X31934 15kÅ PTPH L5101(09/04) 2350 0.3k 41.0 116.0 122.3 46528   7698 0.181 0.002
  • Difference of -8% 
 wiped L5103(09/05) 2350 0.3k 41.0 115.2 121.0 37375   6676 0.197 0.002
X32828 75% PTPH->15kÅ L5105(09/07) 2330 0.2k 40.9 104.1 108.5 57930 11211 0.215 0.002
  • Difference of  3%
wiped L5106(09/07) 2330 0.2k 40.9 103.9 108.8 41514   7811 0.208 0.002
X32827 50% PTPH->10kÅ L5102(09/05) 2350 0.2k 41.0   96.7  100.8 69856 13066 0.207 0.002
  • Difference of -3%
wiped L5104(09/06) 2350 0.2k 40.9   94.5   98.3 55774 10721 0.213 0.002
X32841   30%  PTPH->6kÅ  L5107(09/08) 2360g - -   -   - -  - - -  

====================================
Thickness(kÅ):       5            10                   15
Improvement:      17%    10%  -3%      3%  -8%
by                         Eric    Eric  L.Y.     L.Y.   L.Y.
====================================

Remarks:

(a) For every coated PMT, an additional layer of 100% MgF2 ->250Å was used to protect the P-Terphenyl layer.
(b) Aped is the channel number of the pedestal peak positon in the spectrum, while A1 the channel number of the first photon-electron peak positon.
These two values were derived from fitting with Guass function.
(c) Aav is  the average channel number of the events between L1 and L2, with the definition
L1=30%*(A1-Aped)+Aped
L2=2*(A1-Aped)+Aped
(d) Ntot is the total number of all the events collected, while N> the number of events with the channel number greater than L1.
(e) µ is defined as  -ln((Ntot-N>)/Ntot). Sigma(µ) is the statistical error of µ, which was calcualted from
sigma(µ)=sqrt(N>/Ntot) *sqrt(Ntot+N>)/ (Ntot-N>).
(f) There was some white stain on the coating surface.
(g) High dark noise. About 5-6k  in the beginning with coating. Then after wiped off the coaitng, the dark noise was even higher, about 7k at 2360 HV. So I stoped the measurment on it.
 Anyway, Eric had some results at similar thickness.