Photomultiplier FEU-31

[Henri]

Pin #10 is the photocathode, the pin is placed a little bit inside the ring, you can see the diagram here:

https://eandc.ru/pdf/opto/feu-31.pdf

by the way FEU-31 made for gamma spectrosocpy and scintillation counter, but tubes marked with "A" (i.e. FEU-31A) not passed quality control for energy resolution and sorted for scintillation counter only.

You made my day!!!!!              

OK, now I'm indeed confused...

According to the datasheet you linked, the pin that is a little inside is D2, and the one left from it the Kathode.

But on your layout the inside pin is the Kathode.

As your layout worked, the datasheet must be wrong, but how did you find out?

[Henri]

We need a really small (SMD), rectangular narrow, energy saving, high voltage supply with only a comparator for the pulses for this PMT, to mount this together in a probe

E.g. like this:

https://www.researchgate.net/publication/222720646_A_Cockcroft-Walton_base_for_the_FEU84-3_photomultiplier_tube

[rhelectronics]

Mine just came with printed datasheet, same as attached. Pin #10 is photocathode placed a little bit indise the ring. All other datasheets are not really clear for understanding because they show dot on pin#1 where you need to start counting clockwise and the count will end at the last pin#10.

[Henri]

Mine just came with printed datasheet, same as attached. Pin #10 is photocathode placed a little bit indise the ring. All other datasheets are not really clear for understanding because they show dot on pin#1 where you need to start counting clockwise and the count will end at the last pin#10.

Hi,

my FEU-31 came with exactly the same printed datasheet, but I can not see any of the pins being placed only a fraction of a mm inside the circle. They are all the same. 

Unfortunately, I started soldering yesterday before reading you layout posting, so I'll habe to start over again.

It's so strange they don't make it clear... Maybe there is something in the russian text that we're unable to read.

[DG0MG]

I have the same Datasheet with my PMT and it is not detectable, which is the Pin inside the circle.

Here is a Datasheet of different russian PMTs: http://zapadpribor.com/products/fotoelektronnye-umnozhiteli/datasheet/tekhnicheskie-kharakteristiki-fotoelektronnykh-umnozhiteley.pdf

On page 7 is the relocated Pin #1, which is not the Photocathode:

[rhelectronics]

Can you post a good photo of your FEU-31?

[Henri]

Hi,

I tested it out, and rhelectronic's version works!  The russian datasheet is wrong. 

As I started soldering, I had not read the second post with the PCB layout. So I finished this wiring first, but got no pulses at all. Today I rewired it according to rhelectronic's PCB layout, and now get nice pulses with a 10k load resistor, all the other resistors are 3.0M.

OK, for everyone who has a FEU-31: the recessed pin is the cathode (pin 10 acc. to the datasheet that was delivered with it). If you hold the recessed pin down, right from it is pin 9 (1st Dynode, and left pin 1 (2nd dynode). Then the resistors always cross the center of the tube (zigzag). The result is a fairy small VDN. But everything can be nicely seen in the posted PCB layout.

Thank you all for your kind assistance! 

Henri

[Henri]

Btw. I used -1250V. At -1000V I got no pulses at all, they started at ~ -1100V. But with -1250V it already works great. This is the upper level of my Hamamatsu C4900 HV module.

[rhelectronics]

Btw. I used -1250V. At -1000V I got no pulses at all, they started at ~ -1100V. But with -1250V it already works great. This is the upper level of my Hamamatsu C4900 HV module.

Glad to help it works
As I remember my FEU-31A samples worked with -800V-900V HV bias and I was able to get ~11% energy resolution on 662keV with an old stock 18x30mm crystal.

[DG0MG]

Can you post a good photo of your FEU-31?

Yes.

At this ebay-listing from a russian seller of a Socket "PL23-2P" for FEU-31 the seller says in the second picture, it is Pin #10 which ist out of orbit.
https://www.ebay.com/itm/382443687844
This is in coincidence with Henri's try and my first guess in answer #1.

But the data sheets posted by rhelectronics in answer #11 and me in answer #19 showing Pin #1 is out of orbit. With the explicite description "ФЭУ-31".
There must be an other explanation for this, than "the data sheet is incorrect".
But which?

[Henri]

There must be an other explanation for this, than "the data sheet is incorrect".
But which?

I had the impression that the document you posted was copy-pasted from some scanned catalogues, and that the title was added manually. Maybe it was simply a mistake (there are tons of PMTs listed), and this one has been copied again and again...

On the other side, there was no other FEU PMT in the catalogue that used the "one pin recessed" coding. And the part of the datasheet in the catalogue that was marked as "FEU-31" must depend to a PMT. But which one??

What I really can not understand is why this pin is not marked in the datasheets delivered with the tubes.

But - however - it works 

[Henri]

Btw. I used -1250V. At -1000V I got no pulses at all, they started at ~ -1100V. But with -1250V it already works great. This is the upper level of my Hamamatsu C4900 HV module.

Glad to help it works
As I remember my FEU-31A samples worked with -800V-900V HV bias and I was able to get ~11% energy resolution on 662keV with an old stock 18x30mm crystal.

Maybe mine is also working below with some "finetuning". I simply looked at the scope for the peaks appearing, and that was quite late.

Which value did you chose for the resistors and the load resistor? They did no recommend more than 3M, so I stayed with this, and a quite common 10k Load. But e.g. for a Theremino PMT adapter the VDN would be too low, on the 8 stages you'd need more than 10M on each to get the required >100M - this is  3x the maximum value.

Did you maybe try this, and did you see any disadvantages on high countrates?

11% is not that nice but I'm going to do only do pulse counting with it. My tube is ober 40 years old, so I don't expect more. They are pretty cheap and compact, and the black paint is also helpful.

Have a nice day!

Henri

[rhelectronics]

Henri, I have used 4.7Meg reisistors in the divider, and 1Meg load resistor on anode. 3x10nF capacitors over last dynodes. RC-CR filters are recommended too for gamma spectroscopy. Anyway if you use an audio adapter MCA then countrate does not matter since audio interface is slow and cannot work with countrate above 500 CPS-1000 CPS. You need to make a pulse length about 100us for audio MCA. If you work with fast ADC then maybe you can make pulse short as 10-20us, depend on ADC of course.

For scintillation only, you can use fast comparator to trigger the counter. Try 1Meg load resistor to check the amplitudes and an option to make HV a little bit lower than 1kV.

For the cheapest socket variant, I have used 9pin plastic socket and drilled the 10-th hole with installed nixie tube female pin
https://www.ebay.com/itm/10PCS-9pin-B9A-Plastic-Tube-socket-FR-12AX7-12BH7-12AU7-ECC83-6DJ-6922-PCB-MOUNT/223512230494

[rhelectronics]

Got some FEU-31 and FEU-67b tubes for scintillation experiments 

[rhelectronics]

Not sure it can give good energy resolution for spectrosocpy, will try!