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Re: Rank_Hamamatsu_R878

        Reply to:   RE>Rank_Hamamatsu_R878

A can of worms has been spilt.  
1.  Around 1986 or so Rank came out with an upgrade kit to replace the old
PMT's and head amps (called Plus Kit) to improve the Signal to Noise of the
front end.  At that time the Hamamatsu PMT's #R550-HA for Red and Green and
R878-HA for Blue were installed in the Cell Box to replace the earlier Amperex
PMT's.  These PMT's were pretty quiet except they had a poor transient
response that caused poor depth of modulation at the 400 line and higher
frequencies requiring a lot of high frequency boost in the Afterglow

2.   In 1988 Rank then asked a few users to test a new set of PMT's from
Hamamatsu.  These turned out to be the R8326-HA for R & G and the R2154-HA for
Blue. (Both the 878 and 2154 models were designed for scintillation counting
and have extremely high gain and a spectral response leaning a little more
towards Blue compared to the 8326 and 550).  The R8326 and R2154 combination
was used for years and are still used to this day, I think, in the URSA Gold
(someone correct me here if I'm not up to date).  The 8326 and 2154 PMT's have
a thick lens incorporated on the face of them and a much faster transient
response so the afterglow high frequency tweeks can be turned back down.  

3.   With various tricks to increase the light throughput to the PMT's such as
using TE's Platinum Plus CRT, Rank's "Highlight" kit, third party gate lenses
with bigger F-stops, and improved dichroic elements in the cell box the
scintillation type PMT's in the Blue channel tend to overload at CRT beam
levels above 150 Micro amps and cannot be unfolded at any PEC Gain setting.
For those reasons we use the same PMT in all three channels.  We have found a 
scintillation type PMT does not give you improved Signal to Noise just more of
both and a tendency to overload at higher beam current settings.

4.   The HA designation refers to an integral magnetic shield coating on the
PMT.  Hamamatsu no longer uses this lettering and currently calls that option
-02.  The price for Hamamatsu's R8326-02 has recently gone up from around $600
per PMT to about $950 each (exchange rate I guess).  Their phone # to call
them direct is (USA) 908-231-0960.  I think Rank charges a LOT more for these.

5.   Do not intermix the 550/878 series with the 8326/2154 series.  The
propagation delays are much different and you will get severe color delay
problems if you do.
Good Luck,
Dave Corbitt, Manhattan Transfer/NYC

Michel wrote--->
>I have 3 PMT with the same number, = R550HA. Somebody told me he has >2 PMT
R550HA,  but the third one, on the blue gun, has the type # = >R878....??? The
last time I asked for a "blue" PMT, Rank told me there >was no specific # for
the blue.  They were supposed to be all of the same >type, we just have to
care to install the most sensitive one on the blue >gun.........