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Si-14B (Si-8B) detector wiring

Posted: 06 Mar 2016, 07:04
by wesley

I am new to spectroscopy and I would like to connect Si-14B (Si-8B) with GS-1102-PRO.
Can you tell me what I will need? (Of course BNC connector)

Is photomultiplier needed or it is integrated in the sensor?

Thank you!

Re: Si-14B (Si-8B) detector wiring

Posted: 06 Mar 2016, 07:14
by wesley
I have found this:
147.png (26.69 KiB) Viewed 4787 times

Re: Si-14B (Si-8B) detector wiring

Posted: 06 Mar 2016, 15:52
by Steven Sesselmann

If I am not mistaken that is a pancake detector from Sovtubes.

To connect that to the GS-1100A or GS-1100-PRO all you need is a cable with a BNC at the end, coaxial shielding to cathode and core to anode.

The components on your circuit diagram are already inside the GS.

Note: The Default load resistor in the GS is only 1M Ohm, this will work, but could shorten the life of your tube. If you already own a GS you can easily change the resistor, or if you are planning to buy one I can make it with a 5M or 10M resistor.


Re: Si-14B (Si-8B) detector wiring

Posted: 07 Mar 2016, 07:37
by wesley
Thank you very much!

Do you think that adding additional resistor is possible at the detector side?

I have found that for the best operation of this detector 20MOhm is needed.
We have already placed order for GS-1102-PRO, but later we plan to use NaI scintillator.

Technically I am sure that we can replace resistor (even SMD) without any problem in the device, but I am worried about warranty.

Re: Si-14B (Si-8B) detector wiring

Posted: 09 Mar 2016, 03:04
by geba
Hallo, i have three of this pankake Tubes. I hope You have the data shield.When not, i ammend the translation from russian:
Here is the translation:
Counter Beta radiation SI8B (hereinafter counter) is used to register the soft beta-radiation in radiometric devices.
Climatic performance U3.I.
Solo 15170 Date of manufacture OKT 1990
Circuits connecting the electrodes with the findings
Designation Name of the output electrode
I Free
3 Cathode
5 Free
7 Anode

Basic electrical and radiometric parameters
The slope of the plateau of the counting characteristics,%, not exceeding: 0,3
Sensitivity of the counting rate, 1.3 * 10E12 ... 1.9 * 10E12
Sensitivity of the counting rate (imp / uR): (350 ... 500)
The slope of the voltage-current characteristics,%, not more: 1,25
Amplitude voltage pulse, V, no less than: 20
Own background, imp / s, max: 2
Effectiveness of registration of beta radiation,%: 50 ... 85
Current sensitivity, uA: 8 ... 15 (at P = 12.9 * 10E-10 A / kg (5 uR / s))
Operating range voltage, V: 360 ... 440
Maximum operating speed counting, pulses / s: 3400
Maximum operating current, uA: 18.2 !!
The maximum permissible exposure dose of gamma radiation, A / kg: 21.5 * 10E-6 (for 1 min)
The maximum permissible exposure dose of gamma radiation (R / h): (300) (for 1 min)

Precious metals are not contained.

The content of non-ferrous metals in a counter:
Nickel - 3.6 grams per 4-pin.

Acceptance Information

Counter SI8B meets specifications 0D0.339.388 TU.

TCI Stamp

At re-manufactured _________ date

I. After you remove the meter from the package carefully remove the protective cover and visually check to make sure that the counter has no express

mechanical defects (cracks of mica, chipped enamel).

The counter can be taken only at the base. Is strictly forbidden to touch mica window.

2. The inclusion of the counter is made by feeding the anode voltage 390.

3. During operation of the counter values that determine the mode of operation, should not exceed the maximum allowable value.
Doing so may lead to loss of counters performance.

Aktive aerea; Diameter 6,5 cm =
33,18 cm2

So, it ist reccomended to have an resistor on the anode of 5.1 Mohms (Mega Ohms) Some People suggest, it would better work with 22 Mega Ohms !
But the current must not exceed 18,4 micro amperes (Attention In russian they call it 18,4 mA, but this are not milli amperes, it ist micro amperes.)
So further on bring the resistor to the pankake Tube not to the power supply, because of capacity of the BNC cable !
So solder the resistor direct on the Pin 7 (Anode). The anode must be positive and the Voltage should be not more then 400 Volts.
Do not touch the micra in front.
This tube is not enrergy compensated.

Here is a description of this tube
SI-8B / CI-8b - Sort of the Russian version of the LND 7313. It seems much sturdier due to a thicker mica window. It's also about half the price. I just got this tube but it's now on the comparison charts. Here is a nice translation of the spec sheet and here is a pic of how to wire its socket. I have heard that people are using a conversion rate of 430 - 450 for this tube. I did find this tube to be light sensitive and you should also run it within the specified (narrow), voltage range - 360 - 440V. Higher voltages give suspiciously higher counts. I also found these specifications (from the manufacturer?) that have some new info.
Regarding the load resistor: The Russian spec sheet lists the max current through the tube as "18.2 mkA". This has been commonly translated as 18.2 mA. That would make the load resistor only 22kΩ at 400V. However I found this glossary which defines the Russian "mk" as "micro". This makes the load resistor 22MΩ at 400V which is more reasonable. Note that the diagram in the manufacturer specifications (linked above) show the load resistor at 5.1MΩ. However, I went with the original spec and I increased the load resistor from 5MΩ to 20MΩ. I got ~5% more counts at 20MΩ so I left it at that. I think the less current through the tube the better. So the short answer is that I recommend 20MΩ. ... -supported

It is all english, you will understand it better than me.

best regards

Re: Si-14B (Si-8B) detector wiring

Posted: 09 Mar 2016, 07:20
by Steven Sesselmann
wesley wrote:Thank you very much!

Technically I am sure that we can replace resistor (even SMD) without any problem in the device, but I am worried about warranty.
Wesley, you don't have to worry about warranty, I offer first owners a lifetime warranty, my lifetime :)

That part of the circuit is easily modified, it's all through hole components.

Maybe in the future I will add a 10M resistor with an option to switch.


Re: Si-14B (Si-8B) detector wiring

Posted: 09 Mar 2016, 20:55
by wesley

I am very glad that we have placed the order. I really appreciate such support.
We are doing support in a very similar way with our products and I am very glad that there are still manufacturers with the same enthusiasm and policy.

Thank you very much!

Re: Si-14B (Si-8B) detector wiring

Posted: 25 Feb 2017, 02:37
by PeterJohn48115
Hi..i am new here. As per my knowledge to connect that to the GS-1100A or GS-1100-PRO all you need is a cable with a BNC at the end, coaxial shielding to cathode and core to anode.The components on your circuit diagram are already inside the GS.The Default load resistor in the GS is only 1M Ohm, this will work, but could shorten the life of your tube.

pcb assembly

Re: Si-14B (Si-8B) detector wiring

Posted: 13 Aug 2017, 07:15
by Tishers
I am going to bump this thread (slightly) to add a comment about the series resistor for current limiting and also on voltage ranges;

If you have ever taken apart other probes (the Ludlum 44-7 is a good example) you will find that they add a current limiting resistor in series. If you have a meter where you swap out different detector heads it makes sense to limit current at the probe. Each different type of probe is fairly unique; neutron vs. g-m vs. scintillation vs. ion chamber vs. proportional. When I take a 44-7 and go to a different meter (like a modified CDV-700 with a C connector) I do not need to worry about current limiting the probe.

I am mortified when I see pictures of a GM tube like the Si-8 arcing internally, that is not the intention of how these tubes should operate. You have way too much current on the tube and in addition to wear on the tube (metallic vapor from arc evaporated spots on the anode that causes the tube to become leaky or short out) you also get artificially high readings and the tube will saturate at a very low level. That is a disadvantage of any G-M tube, it takes several mSec for the discharge to clear so the tube can read the next incoming event.

The same is true with ideal and maximum operating voltages. Another example is with gas proportional detectors; For alpha particle-only detection the anode voltage is between 1000-1500 V. If you want to see alpha-beta you increase the voltage to 1700 to 1800 V. If all you want are beta rays you add a thicker window (from a few mil of aluminumized mylar up to 50-100 mil of copper).

Re: Si-14B (Si-8B) detector wiring

Posted: 18 Jun 2019, 00:44
by stamasd
Let me add something to this thread about pancake detectors. I do have a couple of these SI-8B monsters (8cm diameter). One works as expected, the other is a bit more troublesome.

The problematic one seems to saturate and lock over a certain cpm range, and unfortunately that cpm is fairly low (1200-1500). Once that threshold is reached the detector doesn't give pulses anymore, and the only way to reset it to a functioning status is to interrupt the high voltage then connect it back. I have played with voltage ranges from 260-450V, and also with resistor values up to 60Mohm. I noticed that this detector likes a large series resistance, and also voltages somewhat higher than recommended in the datasheet (420V vs recd 390V). Still I can't get it to pulse reliably above 1300-1400cpm. It does it for a minute or two then it locks as above. With the recommended voltage 390V and a 20Mohm series resistor I can't actually make it count above 800cpm.

The other SI-8B I have gets to 10000cpm and above without a problem. I wish I could test with higher series resistors but unfortunately I've exhausted all that I have - I'll order more, but values over 10M are scarce and expensive (so instead I'll just make a long chain of 10M ones). I really want to make this one work. The sources I'm testing with are: 241-Am (smoke detector) 0.8uCi for low energy range, 60-Co 1uCi standard check source for high energy range.