varoquaux@normalesupPhoto Blog of the Little-ICE Experiment
Little-ICE is a side project that I am running for a few month. It is a small version of the main experiment that is going to fly in the Zero-G airbus with the lasers from ONERA. The whole project is 4 months long, to build a test-flight compatible experiment ! So progress should go quickly :->. Oh, before you ask, flight is last week of March.
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28/03/07
And the second flight today.
The MOT fiber amplifier is most probably dying and we pretty much lost an order of magnitude on the power coming out of the MOT fiber. But that was enough to get a decent MOT by raising the loading time from 1s to 2s. We had difficulties with the sequencer. It was really doing completely unexplicable things. The sequences seemed pretty much random on different channels and after some time the sequencer added a lot of noise on its outputs.
I tried many things, tweaked the sequences, undid the changes I had done, all this during the one minute break between parabolas. I also moved channels around on the sequencer, managing to lose a connector (we didn't see it fly by but it is quite clearly missing in action). All I did managed only to get things worse.
After a while it was clear that I wasn't improving things, so I started releasing my straps and floating next to the computer. I went to play in the free flight zone, did a few looping and some mid air swiming (Philippe tells me that on the movies I am swiming forward, and actually going backwards), went back in the cockpit for a parabola (That's a pretty crazy experience, you know, and quite a daunting one).
This afternoon Arnaud and I worked on trying to find out what was wrong with the sequencer. Most of the time when I have difficulties with the sequencer it is due to a bug in the software but today it looked more like a hardware problem.
Well after shorttening a few lines to avoid oscillations and adding a layer of fans on top of it, it is doing fine ! Maybe it was just that the poor thing was overheating in microgravity, as it is only cooled by free convection.
So tomorrow we will try to use the Raman sequence that I quickly coded this afternoon to see some transfert.
27/03/07
Today was the first flight. I wont give to much news as we are all very tired and we need to go to sleep early.
Philippe, Nassim and I flew. All went very well. The MOT was just fine. Nassim was sick and Philippe was slightly sick.
We are all very tired. I need to sleep more. It was an increadible experiment. I will write more on that. We have a lot of work to keep on moving and get more results.
26/03/07
Today was the last day before the flight. The sequencer gave us many troubles and we gave up on running it in autonomous mode. The power at the output of the fiber is fluctuating in a very strange way.
We had the briefing, security check... Everything went well, we just had to tape down a few things.
23/03/07
Philippe joined us and Nassim and him worked on synchronizing the Raman lasers. I work a bit more on the sequences, to allow us to hand-scan a few parameters (including time of flight), and started looking at how to acquire data from the scopes.
22/03/07
This moring the experiment was at 5 degrees celcius ! Power in the lasers was terribly low and we had to ask for the plane's heater to be turned on. So please close the door !
Once the plane reached a decent temperature the lasers worked just well and we had a MOT quite quickly. Our first MOT in the plane !
We worked a bit on the sequences and on the compensation coils. In the afternoon we had nice signal on the photodiode. We tried plugging it in the computer controled acquisition card, only to find out that the card was killing our signal. Indeed our signal was very low (60mV amplitude), but it wasn't noisy at all. The card add loads of noise at 100kHz. We called the SYRTE and they are working on a solution (either an amplifier for the photodiode, or an other photodiode. If this fails we will acquire the signal from the scopes.
21/03/07
Today we loaded the experiment in the plane. We positioned it and started connecting the different racks and testing the equipment. Things had not moved as much as we had thought they would have (the truck that carried the experiment vibrated as hell), but a fiber had been badly damaged. Surprisingly it is still working.
We had a big fright because the hyperfrequency source would turn on. It turned out it was only a switch that had been mounted the wrong way around. Fixing this was just a matter of changing the labels.
20/03/07
Today Nassim had some problems on the road, and he arrived too late for us to load the experiment in the plane, so we tweaked little bit the setup. We had to make sure every single little bit of aluminium was properly grounded. Of course a few where not...
19/03/07
I arrived at Novespace an hour before the experiment. When the ONERA truck arrived we immediately unloaded the racks. It was pissing with raining. Thankfully the driver had backed out all the way to the tent and there was only one meter of shower to cross. Unfortunately that meter was the one where we had to maneuver the racks.
Now they are in the tent, and all is well.
16/03/07
This morning I drove straight to the electrical shop I bought the new UPS. It is a 3U rack, and the current one is a 2U rack, so we will have to rearrange completely the rack number 3. And it is not just a question of moving things up, as the rack is currently completely full. Nassim came around today and with him we move a 1U unit to the side of rack number 3 and re built rack number 3.
The experiment is now in its final state. Tomorrow we pack it and load it into the truck for Bordeaux.
I am looking forward to a nice restful week end.
15/03/07
Today we built a home-made security for the UPS: the emergency stop of the experiment has to power off the UPS also. I thought our UPS had an emergency stop, but there has was a mistake in the manual, and the old version, which was the one we had, did not have such a thing. Bummers !
So Frederic added a derivation from the battery, and I run it in the electrical panel of the experiment. There I installed a relay to switch the battery off and controlled it from the emergency stop button of the experiment (by adding a second set of contacts in the button). The battery is a 72V one, and the relay was a 24V one, so we had to drop the voltage to control the relay. As the relay needed 1Amp to lift the contacts, but only 0.1Amp to keep it up, Frederic designed a small RC circuit to provide enough current to lift, but to limit the current while running. Yes 72V, 1Amp, that's 72Watts, a lot of power. With 0.1Amps that's only 7.2Watts. So I tested the whole circuit and mounted it in the electrical panel, making it all nice and clean, for electrical safety. Once everything was done (2AM) I closed the panel and started cleaning up the tools before going home. Just before leaving I checked things looked OK. I did not feel to much like leaving a big set of batteries with a shortcut. Something smelt hot, so I opened the panel to check out. Yes, indeed, it was the resistances and the capacitors. When mounted outside of the panel they where enough air-cooled, but inside the panel they where heating too much. Yes 7.2W is not so little. Bummers again ! All this work for nothing.
The good news is that while buying electrical components for this setup I had also started ordering a replacement UPS with a remote off input. I had a check from Philippe to buy it if needed.
Nassim is missing in action these days: his daughter was born on Monday morning. Hurray, her name in Ambre and mother and child are both well (although the former is a bit tired).
10/03/07
I had to change the emergency stop button: its polarity was wrong, having it pushed made the experiment run.
I also took a few pictures of the complete setup.
08/03/07
Franck and Nassim are lost deep in thoughts. I can't remember what was wrong, but something was.
07/03/07
Today is little-ICE group picture ! Arnaud came we his 1 year old daughter, as the baby-sitter was away this very morning. So Philippe had to baby-sit her during the pictures...
06/03/07
We hacked a small RF switch into the sequencer, just because there was some room there.
Arnaud sent us some pictures of the fried hyperfrequency source. Impressive !
24/02/07
I have just finished mounting the UPS and the ion pump power supply on rack 3. Two heavy bastards; the UPS is 39Kg heavy, and the ion pump power supply 22Kg. I had to clamp them with eavy duty brackets and to tie them down with straps. Now it is time to go home for a well deserved week-end.
23/02/07
Today we spent the day consolidating the experiment. Nassim has been trapping equipment for hours. He has added a neat multimeter, to allow us to check voltages during the flight. I added the warning light for the lasers.
We also got the rack number 3 from the workshop. We are going to be able to put the experiment in flight layout.
22/02/07
I had just finished installing the computer (it looks cool by the way) when the SYRTE arrived with their hyperfrequency source. Frank installed the software he had written to control the source on the computer while Oualid was finishing the electronic rack.
And it worked ! So now we have a MOT with all the componants for ICE !
And Arnaud and Nassim both look very happy to have IOTA (or should I say IOGS) card.
21/02/07
Today I installed the lifting device to be able to remove the wheels from the experiment and lower it on the floor in the plane. Nassim mounted the Raman doubling stage on its tracks, so that we can pull the stage out of the rack and align it.
16/02/07
We have a MOT ! Yesterday we finally got all the parts we needed to make a MOT. Well today we have it. I couldn't capture it with my digital camera. You cannot see it (yet) with a naked eye, but you can see it very well with an IR viewer.
We are still missing the microwave source from the SYRTE, thought ! They are playing with my nerves. One month till we move the experiment to Bordeau, and Novespace is hassling me about security issues with the experiment... Pfff ! Once this is done I will take some holidays far far away from physics. The SYRTE did send me some pictures of the source.
15/02/07
Arnaud arrived today (finally !) with the fiber-coupler. It is a pretty cool thing (worth 30Keuros !). Arnaud looks happy, does he !
14/02/07
Today we installed all the MOT lasers, including the free air doubling stage, perhaps the most sensitive part of the setup.
13/02/07
Nassim and I are slowly placing all the electronics and lasers in the rack. It is a tedious task as everything has to be well held in all directions as it goes in a plane.
07/02/07
Today I moved the little-ICE cube to the new institut. The workshop finished the rack number two. It took me four hours this evening to fasten every bolt on it !
30/01/07
I have been baking the vacuum system for a while now. Currently I am cleaning out the dispensers by running some current throught them.
23/01/07
Today I finally finished bolting the vacuum system. You can see pictures of the dispensers, the getter pump, and the vacuum system beeing pumped down.
19/01/07
I have been running around the building and to shop all week to hunt for bolts and gaskets. It seems like nothing is left in the whole group to do vacuum. And some nice guy borrowed our provision of bolts and gasket and didn't return it.
I need to reorder stuff, elsewhere next time there is a leak in a vacuum system in the group, someone is going to freek out.
I also had to mill the support I had designed for the vacuum system. The company that built it didn't do exactly what I expected. Bother ! And I milled to fast (in stainless steel) and killed a mill... The technician that can get me this mill changed is on holiday till thursday, which means I have to get the workshop to do this. Hum, I am going to loose time with that.
Well at least I can put things together and pretend I am making progress (I say pretend because almost no ports are bolted, so the work is still to be done). Looks cool though ! What you can see is the main chamber (the octagone, I like to call it), with its stainless steel support (the feet are missing, they are sitting in the workshop), and one of the coils.
18/01/07
The two halfs of the frame for rack number 2 are finished. I am still lacking the 10mm thick baseplate, as the order was lost. It will be there in two weeks, that another painful delay.
Well I hope the frame is strong enough. I drilled through the strut for all those brackets. It gave me more work then I had originaly thought.
17/01/07
Hurray, the vacuum system has finally arrived.
I was going crazy, the company was anouncing delays after delays. I was starting to be rude with the sales rep. So now I can start bolting.
15/01/07
I finally managed to have the breadboard drilled by the workshop.
The structure made of struts is bolted on it with M8 bolts going right throught the breadboard. The frame is supposed to hold a 9G acceleration in case of a crash. Looks good to me.
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