Making a New Batch of Detectors

Scintillation crystals, PMTs, voltage dividers etc...
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Steven Sesselmann
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Making a New Batch of Detectors

Post by Steven Sesselmann » 30 Apr 2015, 08:29

Hi Guys,

I am about to start building a new batch of GS-1515 detectors, just got delivery of 30 spun aluminium housings. The next stage is to get the caps machined, and then carefully fit the caps to the housings. It is necessary to do some individual machining to the caps, as the housings vary by +-0.5 mm, once the caps are fitted, holes drilled and tapped, the housings are sent away for anodizing. The anodizing makes the housing strong and scratch resistant, and gives the detectors a nice finish. Finally the caps are sent away for laser engraving with the model number and brand name.

I usually stock finished housings and assemble the PMT's and crystals as I get orders. Assembly involves attaching the crystal to the pmt with optical coupling gel, and fitting a mu-metal magnetic shield around the PMT, thereafter the housing is lined with a layer of high density foam rubber before the crystal assembly is carefully inserted into the cylinder.

A quality silver plated Amphenol brand BNC connector is fitted to the cap with a rubber o'ring and soldered to the 18 Mega ohm PMT divider with special silicone insulated HV copper wires.

The finished detector is then tested, the resolution is recorded and a screen shot of the final spectrum is saved.
Finally the detector is supplied with a RD174 BNC cable and a copy of the detectors performance report.

For those of you who prefer to roll your own detectors, I usually have some stock of the aluminium housings, and I am happy to sell the blank housings. Drop me and email or check the spare parts section on my web site for details.

Steven
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Detector Housing
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GS-1525
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Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

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brehwens
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Re: Making a New Batch of Detectors

Post by brehwens » 01 May 2015, 07:07

Steven,

It is excellent to know it is possible to order quality housings! Speaking from own experience, I have been lucky having a good contact at a workshop at the university who has made my previous housings. However, as my time in academia is coming to an end,so is my access to this workshop.

Do you provide all the different sizes of housings for purchase?

Can you do some custom work also, for example drill/turn a hole in the bottom if one wants to use a well crystal, or a crystal with some kind of end window?
Karl Brehwens
Eskilstuna, Sweden.

Setup: 5 cm lead castle, 2mm copper lining. Gamma Spectacular Pro 2002, Sound Blaster Live! 5.1,
Primary detector: Scionix refurbished 2x2" NaI(Tl) well detector, 7.5% @ 662 keV

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Steven Sesselmann
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Re: Making a New Batch of Detectors

Post by Steven Sesselmann » 03 May 2015, 17:49

Karl,

There is a tooling cost associated with metal spinning. For each size they make a steel die onto which the aluminium is spin formed, they more or less start off with a round disk and gradually stretch it over the die into a cup. Obviously one can't have any undercuts as the die needs to be removed after spinning, so a shape like the one we need for a 3" PMT would need to be made in two parts.

I have a small lathe and can make minor adjustments in my workshop, but it's not practical for me to make the cylinders myself. As with all manufacturing everything is cheaper by the dozen.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

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brehwens
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Re: Making a New Batch of Detectors

Post by brehwens » 03 May 2015, 18:06

I understand the tooling costs, I was merely asking if all the housings you use for your probe builds are also available as "stand-alone" items for purchase, and to what extent you can make alterations.

For example, can one buy the housing for the 2x2" probe, with a hole turned in the bottom for use with a 2" well crystal?
Karl Brehwens
Eskilstuna, Sweden.

Setup: 5 cm lead castle, 2mm copper lining. Gamma Spectacular Pro 2002, Sound Blaster Live! 5.1,
Primary detector: Scionix refurbished 2x2" NaI(Tl) well detector, 7.5% @ 662 keV

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Steven Sesselmann
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Joined: 27 Apr 2015, 11:40
Location: Sydney
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Re: Making a New Batch of Detectors

Post by Steven Sesselmann » 03 May 2015, 20:33

Karl,

Yes, I could easily cut a hole in the base of a 2" tube or shorten it if required. You find the tubes under Parts and Accessories in the store.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

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brehwens
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Re: Making a New Batch of Detectors

Post by brehwens » 04 May 2015, 06:58

Steven,

That is excellent information. I think your two housing sizes will cover most needs that could arise, and add to this your custom work one should have the housing needs covered!
Karl Brehwens
Eskilstuna, Sweden.

Setup: 5 cm lead castle, 2mm copper lining. Gamma Spectacular Pro 2002, Sound Blaster Live! 5.1,
Primary detector: Scionix refurbished 2x2" NaI(Tl) well detector, 7.5% @ 662 keV

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