Old 05-26-2010, 10:45 AM #49
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Default Re: Need help finding PHR-803T diodes for NASA

For a couple of guys that work for NASA, your grammar is awful.


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Old 05-29-2010, 05:17 AM #50
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Default Re: Need help finding PHR-803T diodes for NASA

isn't the setup going to be in orbit? Isn't it cold up there? I would think that heatsinking wouldn't be much of an issue in orbit. as a matter of fact, the extreme temperatures would end up causing wavelength shifts down
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Old 05-30-2010, 04:03 AM #51
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Default Re: Need help finding PHR-803T diodes for NASA

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isn't the setup going to be in orbit? Isn't it cold up there? I would think that heatsinking wouldn't be much of an issue in orbit. as a matter of fact, the extreme temperatures would end up causing wavelength shifts down
depends... in the shadow of the earth it is yes very cold! but you have to consider there is no air or gas in space to pull the heat from an object convectionaly. plus there are no large solid objects to conduct the heat to either. so that means that the only way to dissipate heat in space would be through means of radiation. a vacuum is an excellent insulator and in many instances heat form components in space must be pumped to a thermal radiator and pointed towards the darkness of space, the heat is transferred from the component, to the radiator and then away via infrared radiation.. hope that helps

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Old 05-30-2010, 04:22 AM #52
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Default Re: Need help finding PHR-803T diodes for NASA

if you need anything from my shop email me with what you want. i can send an invoice through google checkout or paypal. you should be able to use a CC with paypal without having to sign up for an account.
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Old 06-02-2010, 02:50 AM #53
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Default Re: Need help finding PHR-803T diodes for NASA

Hi k-shell,

This may be a bit off-topic, but the design you are using for x-ray production... Seems like an awfully complicated way to do it. Looks like you have to make the x-ray generating vacuum tube anyway (the thing with the MC plate, electron multiplier and target), so why bother with using an optical method to modulate the xray generation? Surely a fairly basic electron gun, with some simple cathode modulation will yield a WAY more efficient, wider bandwidth and simpler design..?
Hell, you could just buy one of Hamamatsu's microfocus x-ray sources, and add some fairly simple modulation circuitry to the cathode drive, and you have a ready to go design, with 99.9% of the tricky work already done for you, and in a commercially fielded product... They can even run off 28 volts, so powering it from the SV's DC bus should also be possible.

Cheers,

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Old 06-02-2010, 01:34 PM #54
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Wink Re: Need help finding PHR-803T diodes for NASA

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Hi k-shell,

This may be a bit off-topic, but the design you are using for x-ray production... Seems like an awfully complicated way to do it. Looks like you have to make the x-ray generating vacuum tube anyway (the thing with the MC plate, electron multiplier and target), so why bother with using an optical method to modulate the xray generation? Surely a fairly basic electron gun, with some simple cathode modulation will yield a WAY more efficient, wider bandwidth and simpler design..?
Hell, you could just buy one of Hamamatsu's microfocus x-ray sources, and add some fairly simple modulation circuitry to the cathode drive, and you have a ready to go design, with 99.9% of the tricky work already done for you, and in a commercially fielded product... They can even run off 28 volts, so powering it from the SV's DC bus should also be possible.

Cheers,

Pete
Keep in mind the weight problem ..... when you have to launch a sat, grams count too
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Old 06-03-2010, 04:10 PM #55
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Default Re: Need help finding PHR-803T diodes for NASA

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Keep in mind the weight problem ..... when you have to launch a sat, grams count too
exactly! we estimate that this entire xray source if designed correctly may only weigh ~40 grams (plus the power supplies and controller components)
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Old 06-03-2010, 04:34 PM #56
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Default Re: Need help finding PHR-803T diodes for NASA

The tube assembly will be light, and comparable in weight to the bare hamamatsu tube, but the real kicker is the HV supply, and associated insulation. I would suggest that this is where the weight will be in your (and in hamamatsu's) design. How many kvp are you looking at for emitted energy? I am assuming fairly soft x-rays, due to the simpler/lighter psu requirements. How many watts output? I assume fairly small, given the opto-electrical method of electron generation...

Cheers,

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