Is there anybody can suggest me how to measure ion beam current of non conduction sample putting inside a Vacuum chamber? Usually, by mixing graphite power with sample, or metallic coating on the surface , sometimes using thin conducting foil on the top of the sample one can measure the beam current inside vac. chamber. Again, using rotating vane chopper one can measure the external beam current, where insulating sample, liquid sample, irregular sample can be irradiated. But, I am interested to know is there any method, just like putting some ring with modification in the path of the beam, is it possible measure the beam current?
How about placing a Faraday cup (FC) with a proper bias at the target chamber. The FC can be place by rotating goneometer or retractable feed through mechanism.
Thanks for your valuable suggestion. This is useful for thin sample or to measure the current of incident beam. I don't think it can solve our problem. I want give some more clue regarding our experiment. One of our user interested to irradiate some electronic gadgets and carryout some in-situ calculation (V-I). Actually, the gadgets is placed on a insulated base with specific holder connected with 28 wires. The sample+holder is placed on the sample mounting ladder. Though, the ladder having biasing facility to collect the current via current integrator , but it will not work, since the base is insulator. The ladder is quite thick, and sample base is thick insulator. In that case how can we measure the current?
How about using a current transformer (CT)? If your ion beam is pulsed beam and not DC beam, simply you can use AC CT. If your ion beam is DC beam, then you can possibly use DCCT. For using CT, you need to add a ceramic gap to couple out the magnetic field induced by the ion beam.
You can find some information in the PDF file available on the web.
http://www-bd.gsi.de/conf/juas/current_trans.pdf
Thanks Dr Zen. Its a really useful ppt. We are planning to try with DCCT for our purpose.
Once again Thanks for the suggestion
Mallick
Dear Mallick,
You need to know that the detection threshold of the DCCT is 1 uA as mentioned in the pdf file.
Do you have higher average current than this value?
Zen
In our Pelletron mechine we can get max 100 nA positive ion current (with slits) on the target. So, I think it will not work. Then what else can we apply..
I also found some information about Squid based DCCT.
Perhaps, Watanabe-san is the expert of this device.
It seems to be applicable for Mallick's purpose, but I thought the cost is too high.
Could you give us some information of the cost of the device, Watanabe-san?
I gave the agreement to your comment scince we need the criogenic system.
Yes you can use B.G in place of DCCT because flux change is expected whenever polarity of flux detection coil is flipping. If you no need fast measurement cycle, it is good for your purpose.
If your beam is a high-energy ion beam for SEE and TID studies, you can possibly use a very thin self-supporting film and measure particle back-scattering in this foil right before the target. You can even perform on line monitoring.
Another possibility would be measuring the particle back-scattering in the target itself. The total number of back-scattered particles would give you a number which is proportional to the integrated beam charge.
Self-supporting thin metal film is very difficult to grow. Some times, we are using thin Al-film (50 micron), thickness is quite high and energy loss is quite high. By the use of thin polymer film few micron as supporter one can grow few Angstrom layer of metal film(Al). Possibly, we can use thin graphite/conducting carbon tape with a ring supporter. Thanks for your suggestion.
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