# ccd with response “time constant” of less than 0.5 ns & maximum “radiant sensitivity” exceeding 10 mA/W

I'm building a Raman Spectrometer.

Update: For this Stellarnet Sony ILX511 CCD. https://www.stellarnet.us/wp-content/uploads/ILX511.pdf

What is its response “time constant”? How do you understand the meaning of "response “time constant”"? Do you think it has response “time constant” of less than 0.5 ns?

Original message:

The following specs are listed under the U.S. Strategic Goods list where export license is required for any electronic item to be shipped out of the country.

Does a normal NIR spectrometer ccd1 have specifications "with response “time constant” of less than 0.5 ns and maximum “radiant sensitivity” exceeding 10 mA/W?

What kinds of items use these specs? Are they typical or only components used in say patriot missile systems?

Quoting from the Commerce Control List (where export license is required):

"a.3.a. Non-“space-qualified” “focal plane arrays” having all of the following:

a.3.a.1. Individual elements with a peak response within the wavelength range exceeding 900 nm but not exceeding 1,050 nm; and

a.3.a.2. Any of the following:

a.3.a.2.a. A response “time constant” of less than 0.5 ns; or

a.3.a.2.b. “Specially designed” or modified to achieve 'charge multiplication' and having a maximum “radiant sensitivity” exceeding 10 mA/W;"

1 Such as this one ... the ccd can detect from 785nm to 1100nm, and so falls under "Individual elements with a peak response within the wavelength range exceeding 900 nm but not exceeding 1,050 nm". I'd like to know if this unit has response “time constant” of less than 0.5 ns or having a maximum “radiant sensitivity” exceeding 10 mA/W;". What do you think?

• Note the (often not so easy to follow) Boolean operators: to fall under this export category it must have ((900 nm < peak response wavelength < 1050 nm) && ((response time < 0.5 ns) || ((specially designed or modified for charge multiplication) && (max radiant sensitivity > 10 mA/W))) Jul 20 '19 at 7:51
• The manufacturer of these devices will always mark them if they are subject to export control in my experience. Jul 20 '19 at 15:05

## 1 Answer

Generally speaking, the specifications that export controls are concerned with are well outside the realm of typical consumer electronics. These are no exception.

A response “time constant” of less than 0.5 ns

This describes an extremely fast CCD which can respond to light pulses in the GHz realm. The Sony CCD you've referenced has an integration time of 10 ms -- it's millions of times slower than what this specification is concerned with.

“Specially designed” or modified to achieve 'charge multiplication' and having a maximum “radiant sensitivity” exceeding 10 mA/W;"

This describes an EMCCD -- an unusual type of high-efficiency CCD used in astronomy and various other applications, sometimes including biochemical research equipment (including Raman spectroscopy!). These CCDs require exotic cooling technology. However, the Sony ILX511 isn't one of these. It's a totally normal CCD designed for use in consumer electronics like bar code scanners -- its use in spectroscopes is incidental. It's fine.

• Ok. If StellarNet use only Sony ILX511. Why are their Raman Spectrometers so expensive at over $13,000? I think these can be built just cheap. I plan to build these. shopstellarnet.com/… – Jtl Jul 22 '19 at 3:39 • @Jtl The optics, the integration work, and calibration don’t come for free. – user39382 Jul 22 '19 at 3:45 • but how could calibration costs over$10,000? I think those can be built for just \$3000
– Jtl
Jul 22 '19 at 3:46
• please check these out.. stellarnet.us/stellarnet-downloads they also used the Toshiba TCD1201D PDA detector 2048 pixels 14um wide by 200um tall, and Hamamatsu cooled CCD detector 1024 pixels 24um x 24um x 62 tall = 1488um tall. What do you think are the integration time of these?
– Jtl
Jul 22 '19 at 3:48
• "I think these can be built just cheap." Please let us know. Remember, to compete with the "so expensive" units, you need to build compact (think Czerny-Turner with custom mirrors), rugged, with built-in A/D converter and USB interface. You'll also need to develop the software to interface with the unit AND display the results.Keep in mind that the rule of thumb for commercial electronics is a physical parts/construction cost 20% of final cost. Bench-mount or optics table won't do. Oh yes, and the system must maintain optical alignment over temperature range. Let us know how it came out. Jul 22 '19 at 3:59