Progress-Use RGA to detect D-D fusion

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Sophie Yang
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Progress-Use RGA to detect D-D fusion

Post by Sophie Yang »

This article will be updated continuously.

Most people in fusor.net have proved their success in fusion by detecting neutrons or activation analysis. In contrast, use RGA to detect the products of D-D fusion has received little attention. Because this is very difficult, a very small amount of helium-3 and tritium will be mixed in a large amount of deuterium background.

This means that your RGA must be equipped with an electronic multiplier instead of just using Faraday cup. The resolution of most quadrupole mass spectrometers in the low mass range is quite poor, and the peak width usually reaches 1 amu, which is not enough to distinguish the target peak well. Considering the above issues, I decided to use mks 835VQM to try to detect D-D fusion products.

First, build a vacuum system to do a simple test. The mass spectrometry chamber is CF35 five-way, Agilent sem35 Diode ion pump controlled by the Agilent 4UHV SIP controller as the main pump, and Edwards EXT555H turbo molecular pump is used to provide the starting vacuum of ion pump.

The mass spectrum chamber is connected with three running RGAs, MKS 835vqm, 830vqm and Balzer QMS200.
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Of course, these devices still belong to me, without the support of others.
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The ion pump will use a huge Fischer connector
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Electrode of ion pump
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830vqm and 835vqm are two generations of ion trap RGA of mks, both of which use electron multiplier. Unlike the old product 830vqm, the electronic multiplier of 835vqm can be easily disassembled and replaced.
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In the formal testing, I will use a new Agilent VacIon plus 55 with higher pumping speed to replace sem35. Before that, I do not intend to destroy the ultra-high vacuum environment inside this new pump.
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Dan Knapp
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Re: Progress-Use RGA to detect D-D fusion

Post by Dan Knapp »

You should take note that people have been deceived into thinking they observed tritium ions in an RGA spectrum when they were actually seeing HD+, an abundant ion in any system using D2. I think if you go through the calculations of how much tritium is produced in the usual IEC fusion experiment, your enthusiasm for using mass spectrometry to detect fusion will be dampened.
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Sophie Yang
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Re: Progress-Use RGA to detect D-D fusion

Post by Sophie Yang »

When browsing other people's articles, I have seen that someone mistook 3amu for tritium or helium-3 produced by the reaction. The report of deuterium cylinder I purchased clearly pointed out that the proportion of HD in it was 1980ppm, which was obvious, the peak of 3amu can also be seen before fusion.

However, the observation of 5 amu DT+ will not be disturbed, which is the only possible method to detect tritium. As an ion trap mass spectrometer, 835VQM has a higher resolution in the low mass range and there is no zero blast. With the electronic multiplier, the gas components of 1ppb can be measured. So I think it's worth a try.
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Richard Hull
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Re: Progress-Use RGA to detect D-D fusion

Post by Richard Hull »

Nice high-end materials you are working with!

There will always be HD in D2. In many fusors operated at the low end with no fancy extras there will always be D2O. None of these will hurt fusion in any manner for the amateur, as they are in such small fractions.

For those electrolyzing heavy water to get their deuterium gas, it is important to work this process carefully as possible higher fractions are possible if the system is either assembled or operated in a sloppy manner.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
William Turner
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Re: Progress-Use RGA to detect D-D fusion

Post by William Turner »

There has been research on advanced mass spectrometers that differentiate between HD D2 and T.

U. Engelmann, M. Glugla, R.-D. Penzhorn, H.J. Ache,
Application of an omegatron type high resolution mass spectrometer for the analysis of mixtures of hydrogen and helium isotopes,
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
Volume 302, Issue 2,
1991,
Pages 345-351,
https://doi.org/10.1016/0168-9002(91)90420-U
Abstract: Gaseous mixtures containing the hydrogen isotopes H2, HD, HT, D2, DT and T2, together with the stable helium isotopes 3He and 4He, can be analyzed with an omegatron, also known as a cyclotron resonance type mass spectrometer. This instrument has sufficient resolution to separate all hydrogen/helium isotope ions, except 3He+ and T+. Main advantages of the combination of an omegatron with an appropriate vacuum gauge as an instrument for quantitative analysis are seen in its extremely low sample requirement, very low memory effects, simple operation, comparatively small overall volume (fits in a conventional glove box), and relatively low price.
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Sophie Yang
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Re: Progress-Use RGA to detect D-D fusion

Post by Sophie Yang »

Next, test the turbo molecular pump.

Only turn on the molecular pump and do not bake the system. After 12 hours pumping, system arrived at - 9Torr.
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Obviously, there are some problems in the system, because under normal circumstances, the pressure should be lower than - 10Torr. Then I found that the problem was on this Edwards WRG vacuum gauge. At the seal of pirani tube, WRG uses an organic gasket with uneven shape, which is incompatible with UHV.This design leads to the fact that WRG cannot be baked and has a high leakage rate, so it is difficult to use in UHV. So we can only replace it.
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Richard Hull
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Re: Progress-Use RGA to detect D-D fusion

Post by Richard Hull »

It is interesting see the trials of someone attempting to pump to 10e-10 levels of vacuum. It is a goal in and of itself. I am just glad I do not have to fight evacuation at that level. All the best in getting to that next decade down in pressure.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Sophie Yang
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Re: Progress-Use RGA to detect D-D fusion

Post by Sophie Yang »

If the correct equipment is used, such as a tandem molecular pump or ion pump, it usually takes only one day to enter - 10Torr instead of ten years.
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Sophie Yang
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Re: Progress-Use RGA to detect D-D fusion

Post by Sophie Yang »

Long time no see everyone. In addition to completing my studies, I am also committed to making more preparations for using RGA to detect fusion, which may take a long time.

While considering RGA systems based on 835VQM and 830VQM, I am also focusing on traditional quadrupole RGA. But their ion collector must be an electron multiplier rather than a Faraday cup. In the past year, I have tried to detect some trace samples using Balzers Prisma QMS200 based on Faraday cups, but nothing has been found.
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Through this spectrum, we can clearly see that when the measured ion current is below E-13A, the Faraday cup will lose sensitivity and the ion current will return to zero.

Therefore, we need a powerful electron multiplier that can provide a gain of E+1~E+6 at a bias voltage of 1~3KV, which will pull the detection limit of the ion flow below the noise level (approximately E-15A). Here I choose to use the Inficon transformer 2.0 with an optional electron multiplier, and it can be seen that the length of the analyzer is twice that of the Faraday Cup version.
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Set the voltage of the electron multiplier to 1KV, repeat the calibration, and you can see the spectrum with a gain of around 100.
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Considering that most RGA cannot be directly connected to the chamber under the pressure of fuser operation, I have started to pay attention to RGA used in high pressure environments, such as MKS's HPQ3S and HPQ2S, which can work stably under E-3Torr pressure. Unfortunately, they do not have electronic multiplier options.
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The HPQ3S analyzer is very small and not as big as hand.
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In addition, I have prepared a third stage ion pump Agilent Starcell55 for the fusor vacuum system, to enhance the pumping speed of inert gases.
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More sensitive neutron detection system.
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Replace with a more powerful high-voltage power supply to provide -70KV, 5KVA high-voltage for the fusor.
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to be continued……
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Richard Hull
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Re: Progress-Use RGA to detect D-D fusion

Post by Richard Hull »

Few here have RGAs. Your work is at an especially high end of perfection in vacuum. Admittedly, for critical work, a scrupulously clean and deep vacuum is needed as well as the added accessory of the electron multiplier for the RGA. These do allow for critical mass determinations in vacuum systems.

However, like you note, in most fusor situations the pressures are high during operation and a special RGA designed for this is needed. The hunt for fusion due to a specific gas type is easily confusing. There are so many species of gas atoms and molecules in a functioning D-D fusion environment.

Your effort is laudable, to be sure. It is far more proper and easy to, classically, just detect neutrons when doing D-D fusion. The fusor is an indelicate and much troubled, violent clash of ions and neutral atoms in velocity space where little fusion is done at gross inefficiency, but done nonetheless.

All the best to you in your advanced efforts in trying to sort out what masses and specific identities of gas molecules are in this tormented environment.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Sophie Yang
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Re: Progress-Use RGA to detect D-D fusion

Post by Sophie Yang »

We have already done enough on the issue of neutron detection, and many people in the forum have better equipment and made more effective results. But just listening to the howling of these neutron detectors (such as GR135, Identifinder…)when the fusor is activated is a bit boring.

In the newly built HDPE neutron moderation chamber, I saw over 100K neutron counts again, hoping that this can activate more materials. Como170 will find them for me.
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