Steve Anderson wrote:Most (but not all) PMTs are sensitive in the shorter wavelength region, blue and UV.
Yes i recall Steve O's PMT colour camera so there must be PMTs at least of some use down to the red looking at the RCA chart this looks to be true .
The PMT i was using in the portable PMT flying spot camera video last post was a EMI 9524 with a S 11 bandwidth i am not sure if the S 11 bandwidth is the same for a EMI tube using a RCA Chart ..i will look into this ..
Looking at the data the RCA PMT spare i have below is a 2060 PMT and should be fine in the green light but is a S11 too...
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Colour of the old scope it does look like it is more a blue green than the standard green , well with that filter screen anyway .
Well the CRT in the scope is a 312p31B couldn't fine any data for it
By the time you get to the longer wavelength of green (the CRT phosphor) they are as good as totally deaf. Silicon is generally the other way around, better at red and IR. Cadmium sulfide (LDRs) has an approximate human eye response, but they're way too slow for this application. There really isn't an easy-to-suggest alternative...maybe a Plumbicon camera tube optomised for green?
The hardest problem is not knowing what the problem is but now understanding whats up i will just see if filter idea works with the current setup ....if it makes no difference i will try the second working PMT i have infact 2 others to test ....problem is the colour of the light so mixing colours might work as with what i think is happening with the scope screen .
An alternative of some sort well as a last resort i still have a few ideas before that ,i have got this far and the colour of light is not going to stop me now .
But that's a real hassle, don't even consider bothering...or (not easy) getting hold of a CRT with a blue phosphor....A P7 CRT maybe possible. It has a short blue flash followed by the very slow yellow/orange afterglow which the PMT will ignore...a suggestion, though not guaranteed. How short is that 'blue flash'? I really don't know, it still could be too long for what you are attempting to do here...
Steve A.
Tomorrow Steve i will look into filter before even changing any thing it might just be an easy fix ,if that works i will test it out on the PMTS wired up ...it doesn't really bother me that much as its just some thing else to learn ..i was confused till today with the results .