Isolation box to measure light source inside (closer to visible light)

[latot]

Hi! (newbie here)

I'm doing a experiment, very simple, in the center of a box there is a light source, a small one, and closer is a photon counter device.

The challenge here, and the hard DIY part is the box.

• The box can not any photon get inside, nor emit any of them.
• At the same time it should not reflect any of them, and there is no problem for a photon going out while the it does not react to emit new ones.

So, a shield box that helps to measure light from inside, this really is over what I know how to do, too much ways to light get into and other reactions that can cause more light, so lets simplify a little, I think is good, at least be able to know which materials are the best for this, the thickness can be tested with the light sensor until there is no incoming signal.

I did some research of this, my ideas are the next ones:

• Mirros: Even if are only for visible light, could avoid IR light if I put them on the outside
• Lead: Has very high density, but I'm worried for its toxicity and there is a effect called Bremsstrahlung, which could cause some particles to emit light internally
• HDPE (High-density polyethylene): Could be a replace of lead, while lead has 11000kg/m^3 this one can have 940kg/m^3, so two layers give us more than one of lead, is cheaper, easier to get and not toxic.

With that materials, my idea would be a box of HDPE internally and mirrors on the outside.

There is still issues, no idea if this would be enough to avoid light, and still IR/Heat is an issue, I could use some materials that has low thermal conductivity, and just buy some time to run the experiment (wait to all the material be at ambient temperature).

So, which materials could help to improve

I'll be using this light sensor:
https://www.hamamatsu.com/us/en/product/optical-sensors/mppc/mppc-module/C13852-3050GA.html

Is there any suggestions for this? would be ideal to know, each material if emits photons, in which conditions it does, this info seems so hard to get, like where can I know which photons HDPE can emit?.

Is good to think, that the sensor can probably pick more spectrum that the datasheet says, just to take it in consideration.

Thx!

 

[berkeman]

If this is for the visible light band, just paint the inside of the box black and be done with it. You still will need to ensure that the electrical feedthroughs are light-tight, but that should not be too hard to do.

 

[BillTre]

I used to work next door to a circadian biology lab. They used plywood boxes painted black to do their light controlled experiments in. Wires going through holes could be sealed using black caulk.
That should work fine.

 

[latot]

The camera is able to pick at least from 300nm to 900nm, is little wider than the visible light band, if black is the only needed could be an option this spray of almost perfect black.

Wood is cheap here, so is a very good option, IIRC also has low therm conductivity.

The camera will pick at least, from 700nm-900nm IR and 300nm-400nm UV.

 

[rbelli1]

Can you share any more information about the photon detector? Do you have a manufacturer name and part number? Have you measured any signals in total darkness?

BoB

 

[berkeman]

Can you share any more information about the photon detector? Do you have a manufacturer name and part number?

Yeah, he shared that in his OP:

I'll be using this light sensor:
https://www.hamamatsu.com/us/en/product/optical-sensors/mppc/mppc-module/C13852-3050GA.html

 

[rbelli1]

Yeah, he shared that in his OP:

Sorry. Next time I'll try reading the whole post.

Is good to think, that the sensor can probably pick more spectrum that the datasheet says, just to take it in consideration.

The spectrum it is sensitive to will be a slope down to zero not ending at a point as seen in the datasheet. There will be some sensitivity past 900nm. Depending on the exact details of the sensor there may be some sensitivity past 1000nm.

Looking at the datasheet tells me that the IR irradiance from a room temperature box will not affect the sensor to any meaningful amount. Does the light source you are measuring emit any significant heat? Does the sensor have to go inside the box? Can you make a hole in the side and seal the sensor into that hole? This would eliminate the sensor's heat output from the test area.

Operating the experiment inside a regular household freezer will reduce the IR photons and may reduce the noise floor. You will want to adjust the temperature to -10C so you don't trip the under-temperature lockout of the sensor or operate it outside of its temperature range. Frosting will be a challenge in this environment.

You could build the enclosure and test without the target present at several temperatures to see what effect this has on the sensor.

Here is a datasheet from sensor itself.

BoB

 

[latot]

mm, the sensor does not need to be inside, while we are able to measure what is inside. Putting it out seems a nice idea, avoid not only light, also other particles that could also cause small light.

I just started checking this case, of a more sensitive photon counter, I was able to confirm that there is low photon emissions, but I do not know in which range they are, so I buy a sensor that is in my budget to continue the testing.

Due to this, I do not know if there will be more IR emissions, or UV, well that is the point of experiments :3
Simplifying that part, is not an issue get measures of IR/UV while they are not from the outside.

A freezer, seems to be a good idea, using it externally it could stop the IR from outside, frosting is a challenge, and avoid freeze what is in side could also be other one.

I have a setup to use several peltier cells to go down the temp, maybe a styrofoam box, and inside other box where we can measure.

This camera is also cooled, so I expect to the sensor do not affect too much, obvs the camera will produce heat.

Seal things is other challenge, there is the idea of black caulk, reading seems it also works as glue, so would be like stick the sensor to the box, does not seems a good idea for this use case. If I use something to connect the sensor to the box, I would still need to seal that, a never ends loop, but maybe is enough, I do not know the behavior of black caulk with IR/UV.

 

[rbelli1]

Sealing can be done with black foam at the interface of the parts you don't want permanently bonded.
Some black materials are completely clear to IR. To avoid that find black foam and caulk that contain carbon black. Carbon will also block UV. To test materials you can build your apparatus and expose to sunlight briefly. Heating of the box may affect the sensor.

An option is to wrap the whole thing in aluminum foil. Be careful not to short out any electrical connections.

BoB

 

[latot]

I can't found any, not expensive foam with carbon black, at least here, they are pretty expensive, and sell in not minor amounts.

How works aluminum here? IIRC it can emits light with some charged particles, but maybe a wood box that is cover in aluminum could be a good use?

 

[rbelli1]

I can't found any, not expensive foam with carbon black, at least here, they are pretty expensive, and sell in not minor amounts.

Carbon black was one possible material but not exhaustive. The foam used to store integrated circuits has it. Many other materials have it. It is a common way of getting black polymers. It may not be advertised as such unless the carbon is a prominent feature. For example, nylon that is black often has it but you have to find the SDS to be sure.

How works aluminum here? IIRC it can emits light with some charged particles, but maybe a wood box that is cover in aluminum could be a good use?

²⁶Al is radioactive but is very rare so the material you buy in the grocery store is not going to be emitting detectable radiation.

BoB

 

[latot]

So, let summarize to know if we are going good.

To block Normal light, use black.

To block UV/IR use carbon, I was able to find carbon paper, is cheap so it can be used.

How is the blocking working for carbon? The light can be absorbed, reflected, transformed.
A normal black thing will just absorb the energy and transform it to IR.
What does carbon here with the energy?
This is a key section to define other aspect of the box, how to avoid the light inside the box to be reflected or transformed to the sensor spectrum.

The box can be of wood, google says (a very bad way to get this info) the thermal conductivity is 0.2~0.1, which would be very good.

My issue with metals like Aluminum is not if it emits by its own, is more when it reacts to charged particles.

Thx.

 

[BillTre]

The inside of the box should also be black.

In fact, I have seen some light control containers with several black baffles so the box doesn't have to be sealed, but things like tubes can go in and out. This does have the possibility to let some photons in. So put it in a dark room or box.

Darkrooms used to be pretty common on universities for reason of film developing, but not so much now in the digital age. They are easy to make if the door is good.

Another thing you might find interesting are to new kinds of black now being made. Ventablack was probably one of the first. It has a carpet of carbon nanotubes perpendicular to the surface that trap and absorb almost all (99.96%) photons that hit them. It is expensive, fragile, and their primary product not available to normal consumers (used for satellites, telescopes, cameras). It also has its own particular production methods. the nanocarbon tubes are grown on the surface that is wanted to be "painted". There are now several competing really black black products out there, including variants from the Vetablack company. At least some can be painted on and maybe available to normal people.



I was interested in this a few years ago and contacted some ventablack engineers and found out some interesting things from them, like its fragility.

 

[rbelli1]

To block UV/IR use carbon, I was able to find carbon paper, is cheap so it can be used.

I think you will find that the paper will have some amount of pinholes that let some light through. I would find a plastic black sheeting and verify that is it colored with carbon. Thicker is better.

How is the blocking working for carbon?

It is absorbed mostly. It is heated slightly and re-emitted as very long wave IR.

My issue with metals like Aluminum is not if it emits by its own, is more when it reacts to charged particles.

What charged particles are you worried about?

BoB

 

[Vanadium 50]

What you want is called a "Dark Box" and you will probably have more success looking that up.

They are typically wood.

You will need to block light from every single crack. This means come combination of foam (styrofoam) plastic right angle brackets, RTV and electrical tape on the edges and corners, and some kind of "plug" at the top.

The inside should be painted flat black and covered in black felt.

Then the whole thing should be covered in black felt before you use it.

If you do everything just right....it still will not work. However, hopefully it will work well emough so you can see where the light is getting in so you can take additional steps. This usually involves lots of black sticky tape.

Think about it this way - for every mole of photons, you only want one to sneak in.

 

[latot]

@Vanadium 50 :O I didn't know its called a Dark Box.

I don't get very well why so much black, a normal black would convert visible light to IR, which is not nice for a Dark Box, this could be improved with other ppl advice on materials.

mm, after some thoughts, is not necessary reduce the photons, I think could be easier instead isolate create a space with constant photon emissions, with that a sensor could measure the changes.

Which properties has styrofoam for this? and what is RTV?

Thx!

 

[Vanadium 50]

You need to reduce the ambient light by 230 dB. That means pluggging every little hole. This is not a materials pronlem. This is a hole-plugging problem.

If you can see a hole or a crack with your eye, it is at least a million times larger than one that will cause you trouble. Plug holes.

 

[Tom.G]

and what is RTV?

RTV stands for Room Temperature Vulcanizing.

It is a Silicone Rubber, usually sold in a squeeze tube like toothpaste.
When exposed to air it absorbs moisture and crosslinks into a rubbery solid in about 24 hours. Working time is usually around 20 minutes. It releases a small amount of Acetic acid as it cures, causing it to smell like vinegar.

Here in the States, it is commonly available in hardware stores and even some grocery stores. Common colors are clear, White, or Black.

Cheers,
Tom

 

[rbelli1]

It releases a small amount of Acetic acid

It is also available in non-acid producing formulations. They are more expensive. You may consider them as you are using it with sensitive electronics. Search for "electronic grade silicone"
One example is black ASI 388. It contains carbon black as a pigment.

normal black would convert visible light to IR

The conversion is due to thermal heating. If you keep the experiment cool then the IR emissions of the materials will remain outside of the sensor's range.

BoB

 

[Vanadium 50]

IR is utterly, completely and totally irrelevant. The sensor goes to 900 nm, which is 3000+ K. Is this a blast furnace.

Let me say this again - as the guy who built a few of these. The problem is simple and not sexy. It's all about plugging holes and cracks. If you can see light through a hole with your eye, it is a million times bigger than will cause your trouble.

 

[latot]

In this case, why even the more basic astronomic camera comes with a IR filter?

 

[Vanadium 50]

No idea. Never bought one. I know that a dark sky is trillions of times brighter than a dark box.

I've built a half-dozen of these. You have built....um...zero. Of course you have superior expertise! I told you what needs to be done. Ignore it if you wish. Its your project.