From: Brown, RM (Bob) - PPD [R.M.Brown@rl.ac.uk]
Sent: 26 March 2007 11:53
To: dgp6d@galileo.phys.virginia.edu
Cc: Dave Cockerill; cox@uvahea.phys.virginia.edu; rjh2j@virginia.edu;
Bell, KW (Ken); cox@uvahea.phys.virginia.edu;
arenton@heplx1.phys.virginia.edu; Peter Hobson
Subject: RE: minor corrections to vpt paper (H:\CMS\VPTx\Rate Tests &
Pulser\newvptpaper.pdf)

Attachments: OPAL VPT10mar 1987 section 6.doc; Brive response.pdf

Dave, sorry for the delay.  I was going to point you to a URL on the VPT web page, but Dave C. has been too busy to post it there.

This material touches on the temperature dependence issue, but we did much more work on it than is reported here.  I have to confess that I have failed to find the original data, even though the measurements were made only twenty years ago.

I hope this stuff may be of some interest.

'Brive' is the town in France where the OPAL VPTs were manufactured.
The firm has gone through various incarnations:
Philips
RTC
and Photonis, (last time I looked).

Bob.

-----Original Message-----
From: dgp6d@galileo.phys.virginia.edu
[mailto:dgp6d@galileo.phys.virginia.edu]
Sent: 16 March 2007 17:09
To: Brown, RM (Bob) - PPD
Cc: Dave.Cockerill@CERN.CH; cox@uvahea.phys.virginia.edu; rjh2j@virginia.edu; Bell, KW (Ken); Cox@uvahea.phys.virginia.edu; arenton@heplx1.phys.Virginia.EDU; Peter Hobson (E-mail)
Subject: RE: minor corrections to vpt paper (H:\CMS\VPTx\Rate Tests &
Pulser\newvptpaper.pdf)


Hello Bob,

I would be very interested in reading your note from the OPAL
experiment!  
Any background reading is always very useful and the subject of VPTs is 
very interesting nonetheless.  Thanks for your comments!

Cheers,
Dave Phillips

On Fri, 16 Mar 2007, Brown, RM (Bob)  - PPD wrote:

> Dave,
> 
> Thanks for the corrected note.
> 
> It reminded me that just 20 years ago (!) we did similar studies on
the
> VPTs used for the ECAL Endcaps on OPAL.
> 
> The points that emerged from those studies were:
> 
> A new tube shows 'hysteresis' when the temperature is cycled, if you
> vary the temperature up or down, you don't reproduce the intital
> response when you return to the starting temperature.  The area of the
> hysteresis loop decreases with each cycle, it is only after a number
of
> cycles that the temperature dependence of the response becomes a
> meaningful quantity.
> 
> The temperature dependence is wavelength dependent. For a bi-alkili
p.c.
> it is negative in the blue region and positive in the green.
> 
> For VPTs, the temperature coefficient shows large tube-to-tube
> variations.  This is is because the thickness of the low-work-function
> coating on the dynode varies considerably in thickness and
composition.
> 
> If you are interested, I could scan in an internal note that mentions
> these points.  (The original was produced by a secretary on a
> typewriter!)
> 
> Bob.
> 
> -----Original Message-----
> From: dgp6d@galileo.phys.virginia.edu
> [mailto:dgp6d@galileo.phys.virginia.edu] 
> Sent: 13 March 2007 20:48
> To: Brown, RM (Bob) - PPD; Dave.Cockerill@cern.ch
> Cc: cox@uvahea.phys.virginia.edu; rjh2j@virginia.edu
> Subject: minor corrections to vpt paper (H:\CMS\VPTx\Rate Tests &
> Pulser\newvptpaper.pdf)
> 
> 
> Hello Dave and Bob,
> 
> I noticed a couple of extremely minor errors in the vpt temp.
stability 
> paper yesterday. Namely, in Sections V and VII there was a missing
zero
> in 
> the error on the temperature dependence of the VPT/Amplifier system.
> This 
> has been fixed and the updated document is attached.  Still wondering
if
> 
> you all have any comments on the paper?  
> 
> Cheers,
> Dave Phillips
> Graduate Research Assistant
> University of Virginia
> Department of Physics
>