refurbishing a Labr3 detector

[luuk]

Hi guys,
I did a full refurbishing and some test with a LaBr3 crystal,
if interested please read the attachment.
Luuk

[iRad]

Very impressive. Both your work Luuk, and the detector. Lucky BOB!!!

[luuk]

Hi Tom,
thanks, yes It's the dream detector for every amateur.

Luuk

[Sesselmann]

Luuk,

Thanks for the brilliance report...

Spectacular results indeed, I am really keen on making an LaBr detector, I know I can get the crystals, but need to research more on the PMT's.

Steven

[luuk]

Hi Steve,
The pmt must have to get the maximum out of such a crystal a sba or uba cathode if not you will loose >1% in resolution, and that would be a shame.
Unforunately these pmt's are expensive a uba 2" cost around 400 , best pmt's come from Hamamatsu look for the extension -100.
Luuk

[Sesselmann]

Luuk,

Yes I agree $400 is expensive, but when you consider the cost of the crystal it's not such a big issue.

I noticed in t=your report that the PMT was significantly wider than the crystal, is this deliberately done so only the centre of the photocathode is used?

I imagine from the point of view of ion optics if electrons released right at the edge of the photocathode might be harder to focus.

Steven

[luuk]

Hi Steve,

Yes a smaller crystal on a larger pmt will give normally a better result, the reason is that the Cathode is not(never) homogeneous special on the edges it gets worse, more to the centre it is always better.
Also LaBr3 is relative fast and the edges of a pmt will give a longer time before the electrons arrive to the grid unless you have a special designed pmt.
In 90% of all detectors a larger pmt will give a little better result, than a pmt of the same size as the crystal.
I made an error in my last mail the sba cost around 400 the uba is even more expensive(>600) but for LaBr3 a sba is sufficient prices are in Euro’s not $.
Do you have already a LaBr3 in your possession?

Luuk