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GAMMA HIGH VOLTAGE

Posted: Fri Feb 24, 2006 5:51 pm
by Steven Sesselmann
Hi Guys,

GAMMA HIGH VOLTAGE RESEARCH:  Model RR200 1.5N.
I have been offered one of these units relatively cheap.

Does anyone know this unit and is it suitable for use as a Fusor input
piower source.

Steven

Re: GAMMA HIGH VOLTAGE

Posted: Fri Feb 24, 2006 5:56 pm
by Q
well, i am not familure with this unit, so i cant say if it will make a good fusor supply. but if it is at a good price, i'd say go ahead and get it. i'm sure there are plenty of other expiriments that you could use that for. (assuming that you are knowlegable about high voltage safety, of course)

Q

Re: GAMMA HIGH VOLTAGE

Posted: Fri Feb 24, 2006 5:59 pm
by Todd Massure
What's the voltage and amperage rating?

Re: GAMMA HIGH VOLTAGE

Posted: Fri Feb 24, 2006 6:07 pm
by Brian McDermott
Assuming the "200" means 200kV and the 1.5 means "1.5mA," I'd say take it. The "N" in the part number means negative polarity, so that's good too.

1.5mA is probably too low for a fusor, but if I were offered a 200kV supply with those capabilities, I'd take it. There are plenty of other experiments you can perform with such a device.

Re: GAMMA HIGH VOLTAGE

Posted: Fri Feb 24, 2006 6:20 pm
by Richard Hester
It's also instructive to calculate the stray capacitance needed at 200kV in order to store 10J, which will kill you if it hits you just right. C = 2E/V^2, where E is the stored energy, and V is the charging voltage. The capacitance for 10J is 500pF - not a lot. Of course, a smaller capacitance (say, 50pF) charged to this voltage will knock the living daylights out of you. This sort of voltage will also charge up nearby conductive objects to dangerous potentials, as Richard Hull mentioned a few years ago (he found out the hard way). If you get this beast, it should be housed in a grounded screen cage in oder to avoid unpleasant/fatal surprises.

Re: GAMMA HIGH VOLTAGE

Posted: Fri Feb 24, 2006 6:26 pm
by Steven Sesselmann
Thanks for the feedback, I appreciate the safety hints too. If this power
supply is rated for 200KV and 1.5 ma., does that mean that it would provide
higher amps at lower voltages or is the power output constant at 1.5 ma.?

Steven

Re: GAMMA HIGH VOLTAGE

Posted: Fri Feb 24, 2006 6:40 pm
by Brian McDermott
1.5mA is the maximum it will supply at any voltage.

Re: GAMMA HIGH VOLTAGE

Posted: Fri Feb 24, 2006 7:55 pm
by Steven Sesselmann
Thanks Brian, that might be a bit low, I thought I would be able to draw
more at lower voltages. Allthough, my Fusor design won't draw as many
amps as the standard Fusor model, as it does not have a grid in the
traditional sense. Still, I would not want to be limited to 1.5 ma. So, I think I
will give this unit a miss, and wait for a unit with a bit more power.

I have a questiuon about safety. In these split power units, would it be
adequate to build a Faraday cage around the voltage doubler and the
Fusor, and to have the controller outside the cage?

Is there any danger of electrocution when operating the control unit?

Steven

Re: GAMMA HIGH VOLTAGE

Posted: Fri Feb 24, 2006 9:09 pm
by Wilfried Heil
You can tap the HV multiplier at a lower stage, where it will output proportionally more current, and disable (jumper) the rest. Say 50kV at 6 mA or 25kV at 12 mA. That´s not what is was designed for, but it will do, if needed.

Re: GAMMA HIGH VOLTAGE

Posted: Fri Feb 24, 2006 9:52 pm
by Steven Sesselmann
Does anyone else have experience with this?

How would this work with the controller, would I just have to double the
amp reading?

Steven

Re: GAMMA HIGH VOLTAGE

Posted: Fri Feb 24, 2006 10:11 pm
by Wilfried Heil
No changes to the controller should be needed, at least if it can display the larger current without assuming a fault condition. The controller displays the actual amp reading, which is usually measured as a voltage drop through a resistor to ground. The voltage reading should be ok as well, it is the true output voltage reduced by a resistive divider.

You should get the schematics for this device, and understand them well, in order not to kill yourself. In my opinion this unit is just too pretty to be used as a Fusor power supply. But it would be great to have one for all kinds of other HV experiments.

Automatically tapping multiplier stages is done in capacitor charging systems, to make them charge faster at the lower voltages and then increasing the number of stages as the voltage goes up.

Re: GAMMA HIGH VOLTAGE

Posted: Mon Feb 27, 2006 3:13 pm
by DaveC
Steven -

The voltage multiplier is a capacitive equivalent to a high voltage transformer. Charge is shuttled around, rather than magnetic fields. So within the limits of the cap sizes and diodes' current
ratings, you can reconfigure, just by tapping a lower level stage.

Tapping a multiplier at a lower voltage WILL allow you to operate at more current. It's not necessary to do anything to the multiplier, other than to make the connection to the proper stage, for the voltage you want.

The divider in the HV output however will normally read from the output at the top of the multiplier. So you can get an approximate voltage reading by just taking the ratio of the voltage you tapped into, to the entire output. Example: Tapped at half the voltage, take half of what the voltmeter reads, etc.

But depending on whether the multiplier is made with larger capacitors at the lower voltage stages, you may not be able to get twice the current at half the voltage.

The ammeter should read the actual current without needing scale factors. But.... the meter circuit may need a new resistor to rescale if the meter range is exceeded.

But be careful... 200 kV is a serious voltage... and can reach and "touch" you from rather far away. With a top hat the size you have there and caps to deliver 1.5 mA, you are up about 20 to 50 times what a Van deGraaff generator of that size would deliver. So the jolt could be lethal.
A nice find... and be safe experimenting

Dave Cooper

Re: GAMMA HIGH VOLTAGE

Posted: Mon Feb 27, 2006 4:33 pm
by David Rosignoli
Richard,

Why 10J? The way I understand it, a certain amount of current is necessary to either stop the heart from beating, or cause it to beat at an unnatural rythym. This current is relatively small (on the order of 10mA I think). If you touch a capacitor with 10J of stored energy at a low voltage, little should happen. (And here when I mean "touch" I am referring to skin contact, not sticking your tongue on some terminals.) I understand the precaution of touching charged objects at a certain potential with a certain stored energy, but what is the origin of 10J?

-Dave

Re: GAMMA HIGH VOLTAGE

Posted: Mon Feb 27, 2006 5:01 pm
by Wilfried Heil
You could connect the top toroid to any lower multiplier stage, in addition to it´s connection to the top of the multiplier, thereby shorting out some of the upper stages. This would keep the HV bleeder network and the measuring resistors working as intended.

Like Dave has described, you may have to change the resistive divider for the current measurement, so that it´s output falls into the range that the controller can display.

As one can see from the image, two different colors of capacitors are used (the top ones are white). I suspect that the lower part of the multiplier has a higher capacitance, to handle the higher current needed there. Another common practice would be to put in several caps (2-3) of the same type in parallel in the lower stages.

The top toroid should have a capacitance of about 20 pF, plus that of the HV capacitor chain, maybe 100 pF in total. This thing could zap someone across a wall.

A notable omission are about 4-5 corona rings around the multiplier (see the Glassman website for similar units). The multiplier is likely to self-destruct without them, at the first arcover. If they aren´t available, you can easily make them yourself out of 16 mm copper tubing.

Re: GAMMA HIGH VOLTAGE

Posted: Mon Feb 27, 2006 6:01 pm
by Starfire
It takes about 75 ma to cause ventricular fibrillation below 50ma will cause pain but normally not fibrillation. The voltage has little bearing. The current path does - in a finger and out a finger on the same hand only jolts, but in one hand and out the other -- what sort of flowers do you like?

-- " It's the mill's that kill and the volt's that jolt "

Re: GAMMA HIGH VOLTAGE

Posted: Tue Feb 28, 2006 12:19 am
by Richard Hester
Dave - I heard the number 10J a long, long, long, long time ago, so I couldn't tell you the origin. I looked on the internet this afternoon, and a document from SLAC also listed the 10J hazardous figure and mentioned it as coming from a DOE document. Of course, the voltage level has to be above skin conduction level before the stored energy will hurt you, but anything above a couple of hundred volts is going to be really nasty at best. If nothing else, it can cause burns (I read a Lawrence livermore accident report citing burns at the 10J level), if it doesn't throw you against the wall or into something that will cause some collateral damage. As with any chaotic event, your mileage can vary widely, up to the ultimate. What I really wanted to point out is that at 200 kV, capacitances one would normally regard as "stray" can become dangerous.

Re: GAMMA HIGH VOLTAGE

Posted: Tue Feb 28, 2006 3:08 am
by DaveC
I was trying to remember the energy used for the De-Fibrillators am thinking it's something like 500 J.

But the timing of the shock in relation to the heartbeat cycle is also important. I think this is where the lower energy/current figures enter in. As I understand it, if the shock occurs in the dead time when the heart is stopped and resting, it may cause the heart to not restart.

Really nice piece of gear, so enjoy and be careful.

Dave Cooper

Re: GAMMA HIGH VOLTAGE

Posted: Thu Mar 02, 2006 9:36 pm
by Wilfried Heil
Here is one currently on Ebay: Item number: 7595813165
Maybe the same one?

Re: GAMMA HIGH VOLTAGE

Posted: Fri Mar 03, 2006 12:49 am
by Richard Hester
Only 300W (200kV/1.5ma) - not much can be done with this fusor-wise. It might make the basis for a dandy little low voltage accellerator, though. Safety considerations would make it eat up a lot of floor space in a lab.

Re: GAMMA HIGH VOLTAGE

Posted: Fri Mar 03, 2006 5:36 pm
by Steven Sesselmann
It appears that the unit for sale on ebay is the same one.

http://cgi.ebay.com.au/ws/eBayISAPI.dll ... 5813165&ru

This may be a silly question, but where would the negative output be on
this unit? Is it from the top of the thoroid or would there be some kind of
massive plug at the back.

Also, I would imagine a 200 kv cable would be massive, so how would
one connect this to a feedthrough?

This would require a bit of thinking..

Steven

Re: GAMMA HIGH VOLTAGE

Posted: Mon Mar 06, 2006 12:33 pm
by Richard Hull
You can be sure that if the supply says NEGATIVE polarity that the torid is the output hot (negative) and that ground or chassis is positive.

There is NO cabling for these! You are to arrange for your own takeoff as these levels! They figure if you buy at this level, you have the skills needed to connect to your app. without their help.

Richard Hull

Re: GAMMA HIGH VOLTAGE

Posted: Mon Mar 06, 2006 5:17 pm
by DaveC
Some multiplier type power supplies, DO have a bipolar output, that ie + and - HV, they will have a high voltage termination like the one on the Gamma supply, for EACH polarity.

I know of at least one xray HV supply which has a bipolar drive...which minimizes the insulation issues since an xray tube can have a cathode at negative hv and the target at positive hv.

But as have already been said, each hv output must have appropriate terminals for the rated voltage.

Dave Cooper

Re: GAMMA HIGH VOLTAGE

Posted: Tue Mar 07, 2006 10:57 am
by Richard Hull
Taking another look at this simple system one sees no place for a 200kv plug of any sort. It is obvious the toriod is the output, plus or minus, you will have to touch it to get your juice. Any plug type connector terminal block to a cable that will handle 200kv will be sunk in a lot of oil. The toroid allows for simple air connection via smooth often chromed piping. A huge percentage of such systems are AIR connects as they are cheap and small.

Richard Hull