This Advent during the 24 days leading up to Christmas I thought it would be fun to have a quick introduction of scientific apparatus, in particular tools used in atomic physics research. This is a way to say thanks to their hard work for our research, and a look at how many things are really needed to make a laboratory work!
- Day 1: Acousto-Optic Modulator
- Day 2: Ion Pump
- Day 3: Photomultiplier Tube
- Day 4: Vapor Cell
- Day 5: Analog-Digital Converter
- Day 6: Magnetic Field Coils
- Day 7: Optical Fiber
- Day 8: Electro-Optical Modulator
- Day 9: CCD Camera
- Day 10: Ion Gauge
- Day 11: Residual Gas Analyzer
- Day 12: Arbitrary Waveform Generator
- Day 13: Optical Reference Cavity
- Day 14: Wavelength Meter
- Day 15: Zeeman Slower
- Day 16: Optical Table
- Day 17: Power Meter
- Day 18: Atom Source
- Day 19: Frequency Standard
- Day 20: Diode Laser
- Day 21: Optical Isolator
- Day 22: Lock-in Amplifier
- Day 23: Optical Frequency Comb
In this final post of the advent calendar, I’d like to to showcase the laboratory itself, as a lab is much more than just a room to do stuff in.
The quality of a laboratory setup can even make or break experiments, but at the very least, it has a big effect on how quickly and easily can we progress during the research. Bad design can waste time, but can also create issues that are pretty hard to debug (eg. problems with the electrical system, or the lab lighting interacting with sensitive equipment inside the vacuum system). I don’t think I have the answer of how to create a good laboratory, most researchers go about doing that based on experience, but I’d like to highlight some of the aspects that need to be taken into consideration when setting up a laboratory.
Air conditioning is a major part of good lab – major both in difficulty and in cost, usually. A lot of the equipment requires stable temperature, much more stable than in an office or a home. A good air conditioning would keep a stable temperature, same across the whole lab, all this without much (or any) wind as airflow also affects devices. In the meantime electronic devices will heat their neighbourhood, airflow blocks around the optical tables can make air conditioning ineffective there, and the system has to be able cool when the outside temperature is high (in the summer) and heat when the outside temperature drops low. Standard temperatures are in the region of 21 to 23°C, and whichever it is, have to be kept with better than ±0.1°C variation.
Lighting is another major issue. Putting lights on the ceiling is one thing. Also have to consider how to break up the lights into segments as which parts of the lab should be illuminated as a single unit. Need to take into account where the light-sensitive equipment will be, how will we need light when working in the lab (e.g. main lights off, but a desk lamp near the control computer – will that affect the experiment?). Another issue is light coming from the outside: is there adequate blocking of such leaks?
Vibration is an issue that optical tables supposed to take care of, but their job can be made more difficult if the architecture of the lab is not ideal. How will the building move around the lab (seriously), what other mechanical changes are nearby (is there any elevator, metro line, tram)? The tables go a long way, but some experiments need more than that, so we have to know our requirements.
From the point of usability, sett up storage areas well helps a lot. A big part of the lab is storage, as the experimental setup is constantly changing and need adjustments. Where the mechanical pieces (screws, optical mounts, tools), the optics (lenses, mirrors, waveplates), the electronics cables, optical fibers, spare equipment (oscilloscopes, voltmeters), where are the documentation and user manuals for all these?
Sometimes signals are coming from outside of the laboratory such as a cable going to the rooftop to a GPS antenna, or an optical fiber running to another laboratory which provides a specific experimental beam. Connecting to the outside needs some care, due to light, air conditioning, extensibility considerations. Run a pipe between labs? Drill a hole into the wall? Run under the floor? It all depends on the specific situation.
The arrangement of the optical tables and overhead racks that usually hold the experiment’s electronics is a very practical concern. Usually the requirements focus on practicality, such as do we have enough space, can we reach all the parts of the storage area, will the rack be able to hold the weight?
Laser safety is a core issue as one can be hurt very easily with lasers. For lower power lasers reasonable optical blocks are usually what it takes to be okay on a certain level. To do things properly, though, all labs should have an interlock systems which shut down all lasers in the lab if someone unauthorized comes in (e.g. the door is opened without an entry code). This is to make sure that people not trained in laser safety can’t wander into a dangerous environment.
There are also resources coming from outside of the lab. The most important is power, and knowing the laboratory’s power arrangements can save a lot of time in debugging strange issues! Some equipment needs “clean” power lines that are low noise and backed up by an uninterrupted power supply. Other equipment are fine on the “normal” lines, and should not mix the power lines for these two. There are also water lines for cooling, and compressed air lines for optical table floating.
All the experiments are controlled by computers, so where to place them, how to provide networking, how to use them to run the experimental sequences is another consideration.
Finally, work spaces are needed too, and they are often in another room, so that they don’t interfere with the sensitive equipment (noise, dust, etc…). Most labs need some electronics and mechanical workshop for simple things. For more demanding projects there are usually workshops elsewhere, shared by the labs across the whole organization.
This is the end of this atomic physics advent calendar. If you have liked it or have any comments, feel free to send me an email at email@example.com! I had fun writing it, and now wish all of you a really Merry Christmas!