also new here

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keuleeule
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Re: also new here

Post by keuleeule » 03 Nov 2016, 11:00

No real problem, I have everything ;) and soldering is not that big issue.
but not realy knowing what I´m doing is...
So I can replace all 169k to 1-1,2M, what is about the 260k, the 100R and the capazity? I leave it in? Is my drawing correct?
Didnt found any drawing of my PMT so far.
If the Voltage divider will still match with my PMT I will do it of course.
So I´m pretty sure to order asap a driver from you - if I will be ready with soldering I will still wait days and weeks until the driver arrives from down under... I still need to choose the 2000 series as the handwritten 1500V+ is more than the 1000series can offer - no problem.


In the meantime I copied the "large Harshaw" but I found strange connections... (resistors were not soldered directly on round PCB on top, they were extended to a rectangular PCB in the "camera housing" but:
Unfortunately all the wires to the PMT were drilled, as wenn PMT was turned cables got stretched and ripped off. I was just able to found two still connected, BNC ground was over 0,56M to PMT Pin 10.
BNC hot pin was over a 1,2M, a 0,56M and a 0,82M to PMT Pin2, all other resistors are at 0,56M.
So that circuit looks totally different.
I assume the large one should be read more, so goal is to drive the fatboy - then comparing to the small one.

Thanks so far for all your help - still in the introduction column.
regards, Kolja

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Steven Sesselmann
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Re: also new here

Post by Steven Sesselmann » 03 Nov 2016, 12:17

Kolja,

The 14 pin divider scheme is pretty simple it goes: K - 2R - R - R -R - R - R - R - RC - RC - RC - A

As it is just a voltage divider the value of the resistors are not critical as long as they are the same.

You see it should have 2R on the first stage between cathode and first dynode, this increases the gain at the first stage, some PMT's have a focusing grid between cathode and first dynode and then you will usually have a 2R trim pot to adjust the grid voltage, but setting the pot to 100% gain gives the same result as 2R.

The capacitors don't change, so you can leave these in place.

You can find the optimum voltage for your detector by plotting a series of count rate experiments at different voltages, this will reveal a voltage plateau over which your detector count rate remains relatively unchanged. The optimum voltage is somewhere in the middle of this plateau.

The Harshaw detector seems to have 056M so a total resistance of 6.7M which will work fine with the GS, but just be aware that the actual voltage will be about 7/8 of what you see on the display.

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

keuleeule
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Re: also new here

Post by keuleeule » 07 Nov 2016, 10:40

Steven Sesselmann wrote:The 14 pin divider scheme is pretty simple it goes: K - 2R - R - R -R - R - R - R - RC - RC - RC - A
Whereas the RC goes to ground, and K is Pin 14, A is Pin 11, 12 is unconnected, and 13 is a possible grid...

I study a picture from http://www.ortec-online.com/download/266.pdf

So far completely unclear for me how the signal is connected to your HV in GS 1100pro
In GS2000 there is the chance to connect HV and signal.
How should I proceed with the signal if I go for the GS2k ?
and how if I go for the Gs1100?
thanks and regards, Kolja

keuleeule
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Re: also new here

Post by keuleeule » 07 Nov 2016, 10:44

and a correction, the massive BNC connector isnt a BNC, its a MHV https://en.wikipedia.org/wiki/MHV_connector

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Steven Sesselmann
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Re: also new here

Post by Steven Sesselmann » 07 Nov 2016, 11:53

Yes, single wire detectors may look a bit like magic, but I can assure you it is just simple electronics.

The BNC cable supplies a high voltage bias to the anode which is inside the vacuum tube, almost no current flows through the anode and a very small current flows through the divider on the outside. When a gamma ray hits your detector it scintillates and emits a few photons, which in turn knock a few electrons out of the photocathode in the PMT, these electrons multiply about one million times on the way down to the anode and when all those negative electrons hit the positive anode there is a sudden voltage drop for a couple of milliseconds. This sends a wave back down the coaxial cable to the GS somewhat like plucking a guitar string, and inside the GS we listen for that wave through a capacitor connected to the HV line.

Your cheapest option is to change the MHV with a BNC if your detector runs at low voltage, but if it needs more than 1000 V you may be better to change it to an SHV which is the modern version of the MHV.

SHV stands for safe High Voltage, and it is designed to prevent you electrocuting yourself. The SHV design ensures that the ground connector on plug and socket touch before the HV connects.

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

keuleeule
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Re: also new here

Post by keuleeule » 09 Nov 2016, 02:16

Steven Sesselmann wrote:It is not just the cost of the SHV connector on the GS, but also the cost of cables...
wow, Thought it would be easy to get those SHV, but even in my company they have them under control.
There are some in China, but I had too many issues with Chinese products, so I go for new/old stock german ones at
http://www.helmut-singer.de/stock/-1629440792.html now.
Do not misunderstand as advertising please.
They also provide plugs, so I will also search cable which withstand 10kV to solder myself.
Kolja

keuleeule
Posts: 48
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Re: also new here

Post by keuleeule » 29 Nov 2016, 06:47

keuleeule wrote:
Steven Sesselmann wrote:The 14 pin divider scheme is pretty simple it goes: K - 2R - R - R -R - R - R - R - RC - RC - RC - A
Whereas the RC goes to ground, and K is Pin 14, A is Pin 11, 12 is unconnected, and 13 is a possible grid...

I study a picture from http://www.ortec-online.com/download/266.pdf

So far completely unclear for me how the signal is connected to your HV in GS 1100pro
In GS2000 there is the chance to connect HV and signal.
How should I proceed with the signal if I go for the GS2k ?
and how if I go for the Gs1100?
thanks and regards, Kolja

guys, a quick question,
regarding Stevens picture Image
in post http://www.gammaspectacular.com/image/c ... 00x800.JPG

is Pin 13 connected to Pin 14 ?
GND is K (Cathode)

Thanks, Kolja

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Steven Sesselmann
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Re: also new here

Post by Steven Sesselmann » 29 Nov 2016, 10:54

Kolja,

Yes on the single wire (and ground) divider pictured above pin 13 is wired directly to pin 14.
So far completely unclear for me how the signal is connected to your HV in GS 1100pro
In GS2000 there is the chance to connect HV and signal.
It's very simple, the load resistor and coupling is on the GS side, so when a pulse of negative electrons strike the positive anode it causes a brief voltage drop on the anode causing a pulse to travel down the cable and into the GS where the pulse is picked off with a capacitor connected to the line. Think of of it like plucking a guitar string at one end and listening to it at the other end.

In a two wire detector the capacitor is inside the detector (closer to the action) so the pulse goes back to the GS in a separate cable.

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

keuleeule
Posts: 48
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Location: Hamburg/Germany
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Re: also new here

Post by keuleeule » 29 Nov 2016, 18:42

Ok, fine, thanks a lot Steven.
Got confirmation yesterday that your parcel arrived Germany. So Im really exited now.
Finishing today the pmt divider and hope the gs2000 will arrive.
Will see if I get a spectrum out of my detectors...
regards, kolja

keuleeule
Posts: 48
Joined: 31 Oct 2016, 09:09
Location: Hamburg/Germany
Contact:

Re: also new here

Post by keuleeule » 05 Dec 2016, 06:56

Well, my GS2000 arrived, YEAH! Thanks Steven.
This weekend I connected the detector to the GS2000 but got in trouble with my new USB Soundcard.
So changing over to a PC with internal Soundcard which gave much better results, but still not successful.

I got a significant change in Sound, so pulses reach the PMT, but I do not get any spectrum.
I watched the introduction of Steven several times,
https://www.youtube.com/watch?v=Mp0QYHiS7lU but just get a strait spectrum.

Strange and different to Stevens introduction my audio pulses, they seems not that quite well triggered in the middle of the window, and even not that high.
attached my spectrum. maybe a bad rookie mistake, but think the crystal´s end of life maybe... :(
any comments?

1.000.000 pulses,
Cs137
1500V
with my small detector.
0.5cm lead
divider:
between K and 1Dyn 2MOhm, all others each 1MOhm. between 7th, 8th, 9th, 10nF 3000V to ground. HV direct to Pin11, 13 and 14 bridged ground, 12 open
Attachments
first_spectrum@1500V_Cs137.png
first_spectrum@1500V_Cs137.png (99.48 KiB) Viewed 3048 times

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