What has James been up to?
James Millen

All the time! Writing my thesis and papers. Please check the news page for, er, news!

1st - 5th November 2010: Went on holiday and stayed in a treehouse in the Scottish Highlands.

25th - 29th October 2010: Back to writing about spectroscopy of our Rydberg gas, constructed a 6-channel MQDT model for the strontium S states, made some nice graphs, you know, that kind of stuff!

18th - 22nd October 2010: Visited Peter Barker's group at UCL and Michael Kohl's group at Cambridge to give a talk.

11th - 15th October 2010: This week our paper on two-electron excitation of an interacting Rydberg gas was accepted to Physical Review Letters! I also did some outreach at Belsay Hall in Northumberland. Slightly manic being the only volunteer at the "Making Architecture Count" event for 90 school kids!

September 2010: News will be thin on the ground. Writing a new paper about our Rydberg spectroscopy, writing bits of my thesis, and doing some interaction calculations.

6th - 10th September 2010: We attended the "Cold Rydberg and ultra-cold Plasmas 2010" (CRYP10) conference at the Max Planck Institute for the Physics of Complex Systems (MPIPKS) in Dresden. We presented this poster, and Matt gave a talk. I think I can safely say our work was well received, and gathered some interest!

30th August - 3rd September 2010: Preparing for a conference in Dresden next week. This has mainly involved making a poster!

23rd - 27th August 2010: Submitted the paper, to PRL. arXiv submission can be found here: http://arxiv.org/abs/1008.4512.

9th - 20th August 2010: Writing writing writing!

2nd - 7th August 2010: Writing writing writing...with one distraction. I helped at the Bang goes the theory roadshow at the Hartlepool Tall Ships festival.

19th - 30th July 2010: Writing up our results! Doing fitting and analysis of the autoionization spectra using Mathematica, amoungst other things!

21st June - 16th July 2010: Taking the last of the data for our study of the Rydberg gas using autoionisation. Autoionization spectra, lifetimes and Stark maps were measured for the 5s56p and 5s54f states. We also did a study of the effect of varying the Rydberg laser power on the population of the 5s56d and 5s54f states. Phew!

14th - 18th June 2010: I've been on holiday to Pisa, and had a good look around Tuscany. I succeeded in neither tanning or burning! Success!

7th - 11th June 2010: We can now calculate interaction energy shifts with atomic separation, can compare simulations to our own data, and get a handle on population transfer.

31st May - 4th June 2010: Using radial matrix element generating code to create Stark Maps for strontium Rydberg states. Can calculate energy defects between pairs of states so we can work out whether population is transferred between different angular momentum states.

24th - 28th May 2010: Started to calculate some atomic properties of Strontium around the states we've been looking. Main challenge has been working out angular matrix elements for interactions between atomic states.

10th - 21st May 2010: I went camping in Wales. Camping is ok at best! Also went to see some bands. Jonsi, the singer from Sigur Ros, put on an amazingly pretty live show, and Liars were nuts as ever!

3rd - 7th May 2010: Plenty of data to analyze! Sifting through the data we've taken and tying up some experimental loose ends.

26th - 30th April 2010: A heavy week of data taking! We spent the whole week investigating the evolution of the autoionizing spectra over time.

19th - 23rd April 2010: This week we explored different regions of Rydberg atom density to find the best region in which to perform our experiments.

12th - 16th April 2010: We spent this week getting a handle on using a diode at 408nm to replace the pulsed dye laser for performing autoionization. We've taken a stark map, some lifetime measurememts and an autoionization spectrum.

5th - 9th April 2010: Back into data taking! We took a Stark Map of the 56D state, and have been re-studying lifetime measurements. Also, on Monday went to see the most incredible band (And So I Watch You From Afar) in Newcastle.

29th March - 2nd April 2010: Testing the effect of the 408nm diode, and how it is different from the dye laser. Also, took a trip down south for the Easter bank holiday, seaside fun in Southend!

29th March - 2nd April 2010: Testing the effect of the 408nm diode, and how it is different from the dye laser. Also, took a trip down south for the Easter bank holiday, seaside fun in Southend!

22nd - 26th March 2010: Started writing a paper! Also preparing to retake data using a diode laser to autoionize instead of the death (pulsed dye) laser.

15th - 19th March 2010: Happy National Science Week! We delivered our workshop to five schools in five days! It was intense, but very successful. Hopefully pictures and feedback will appear on our outreach page.

February 2010: Vast ammounts of my time have been taking up preparing for our big outreach project. You can see the website for the project here: here. Of course I have still been analysing data as well, in particular investigating saturation of our ion detector (MCP).

25th - 30th January 2010: After taking a breather following a heavy run of data taking, we have been analysing our data. I also went to Moorside school near Consett to give a talk on going to University.

11th - 25th January 2010: After the Christmas break, Graham and I spent 25 hours a day, 8 days a week in the lab performing autoionization experiments with the pulsed dye laser.

7th - 12th December 2009: The newly upgraded 412nm laser has been set up so we can go on to perform Rydberg experiments at high n (n = 40-ionization).

30th November - 4th December 2009: Our 412nm laser has returned from Germany, having been upgraded from 8mW to 70mw! This week I went to the ATP Nightmare Before Christmas music festival at Butlins in Minehead. By far the best band were Lightning Bolt. Amazing!

23rd - 28th November 2009: Most of this week was spent refilling our strontium dispenser cell. I found out that sometimes strontium smells like wild garlic.

16th - 21st November 2009: I did some theory on the work we have been doing, and started to refill our strontium dispenser cell, which had run out of fuel!

9th - 13th November 2009: We saw our first autoionization signal! Upon shining the light at 408nm onto the atoms when they are excited to the 5s20s 1S0 state we see a dramatic increase in the ion signal as the second electron is excited. Various investigations into this phenomenon were carried out.

2nd - 7th November 2009: This week was dedicated to our 408nm diode laser. A grating was fitted and the threshold lowered. The output was then aligned through an optical isolator.

26th - 30th October 2009: Put a diode at 408nm on the bench, which will access an autoionizing resonance. Also took half the week off to go down to London, mainly to see the amazing Efterklang + full orchestra gig.

5th - 9th October 2009: Finished off taking data for the 5s18s 1S0 and 5s18d 1D2 states, and have left the lab for now to do some analysis. Also did some outreach at Durham Cathedral, teaching KS3 kids about the maths of architecture!

28th September - 2nd October 2009: Our pixelfly camera wa fully integrated into the experiment, resulting in our LabView colde being extremely versatile. I also wrote a piece of LabView code that can stabalise our laser. Using the camera the effect of density on our ion creation was studied.

21st - 26th September 2009: A lot of time was spent analysing older data, and the rest of the time was taken up studying the 5s19s 1S0 and 5s19d 1D2 states.

14th - 18th September 2009: This week I have been studying the transition to the 5s18d 1D2 state, which we believe is an autoionizing resonance. We had to install a new Acousto-Optic Modulator to do this.

7th - 11th September 2009: I was at the QuAMP conference in Leeds this week presenting a poster (see News page).

31st August - 4th September 2009: I have mainly spent my time creating a poster and reading up for the QuAMP conference in Leeds next week.

24th - 28th August 2009: I spent some time analysing some previous data (Rydberg fraction data and ion production). We also saw EIT in our vapour cell, and the first signs of what we believe to be autoionization in out MOT.

17th - 21st August 2009: Our purple laser has sadly been flown back to Germany (to get a serious overhaul!), so no more ionisation experiments of this nature for a while! I've started the long process of data analysis, plus trying experiments with a laser at 410nm, looking to do some EIT on the atoms in our MOT, and look at autoionising resonances.

10th - 14th August 2009: Since we had no mechanical shutter available, we performed cleaner experiments using a technique we've dubbed "Stark shuttering", and done more accurate investigations into the nature of our ion creation process. I also went on a training day in London for an event doing science experiments on the beach for children!

3rd - 7th August 2009: Two big results this week: Firstly I created a Stark map around the n=80 Rydberg states in strontium, and secondly I extended our spectral data to create a more full quantum defect plot.

27th - 31st July 2009: The majority of this week was spent investigating a curious second ion peak evident when our electric field switches off. Ideas as diverse as noise, stark resonances and plasma trapping have been thrown about. Other than that I investigated the ion signal on a long time scale with the trapped atoms in a steady state, i.e. the current Graph of the Week.

20th - 24th July 2009: We did some preliminary experiments on the origin and nature of the ions we are creating. We found that ions hang around for a very long time (many milliseconds), but the creation process of these ions is fast (10μs).

13th - 17th July 2009: Some experiments on polarisation of our Rydberg excitation lasers were carried out. The rest of the week was spent noticing, and investigating, the charge that hangs around for a long time in our experiment.

6th - 10th July 2009: The computer control was used to take a saturated absorption spectrum, so that we could check the frequency response of our laser/wave meter was well understood. Apart from this a third laser system was added to our now very busy optical bench!

29th June - 3rd July 2009: This week was almost entirely taken up with writing LabView. Our oscilloscope and wavemeter are now fully integrated into the program, so that we can control and read the frequency of the lasers, and directly read out data in a number of forms.

22nd- 26th June 2009: The laser has been brought under computer control, and the Rydberg experiments are being carried out by exciting more population using an on resonant probe beam rather than the MOT beams for the intermediate step. We've begun looking at polarisation effects.

15th- 19th June 2009: Wasn't in the lab much this week as I had some time off for my birthday! I have, however, found out that Manchester is a lovely city.

8th- 12th June 2009: Pushed right to the limit of the visible rydberg spectrum in the current experimental configuration, hitting somewhere near n = 135, and assigned some lines!

1st- 5th June 2009: A large section of the Rydberg spectrum was taken, and tentative steps into quantum defect theory have been taken to assign energy levels to the lines.

25th- 29th May 2009: Big news, first Rydberg ion spectrum seen!

18th- 22nd May 2009: Frustrating week of computer and laser problems. Ion signals can now be normalised by the number of atoms involved, and we've started using averaged ion signals as our single ion counting capabilities have been saturated.

11th- 15th May 2009: Investigated the effect of probe detuning on ion production (not much of one!), and also the effect of the accelerating "grid" voltage produced in front of our detector. Found some saturation of our counting device so will have to switch to some manner of integrated signal method.

4th- 8th May 2009: Endless ionisation experiments and analysis! Also have done some 3D electric field calculations using the MatLab code you can find on the Documents and Publications page.

27th April - 1st May 2009: LabView decided to annoy me this week, so it got a good fixing. More ion counting experiments sepeating the electric field pulses from the light pulses.

20th- 24th April 2009:Absolutely fascinating pulsed electric field experiments been done. Don't understand what's going on at all, but it looks interesting!

13th- 18th April 2009:Been getting very bizarre results from ion counting with electric fields on for a long time. Some calculations of charge dynamics overdue methinks.

16th March- 10th April 2009: My time has been very fractured. When I have been at work I've been taking spectra of our trapped, cold strontium. I've also beautified the LabView.

9th- 13th March 2009: On Monday I attended the "SET for Britain" competition at the Houses of Parliament, and did not win! Other than that LabView code was written to enable analogue control of the experiment.

2nd- 6th March 2009: Further study has been made of what happens upon ionising our cloud of strontium. I also spent a lot of time preparing my poster for the "SET for Britain" competition, and aligning my first ever single mode fibre.

23rd - 27th February 2009: The experiment has been refined to work on a microsecond timescale. We've observed short bursts of ions.

9th - 20th February 2009: I've been on holiday in Sweden! If you're really bored you can see some pictures.

2nd - 6th February 2009: The electrodes in the chamber have been used to increase ion yield, meaning that the last piece of the apparatus has been tested and utilised.

26th - 30th January 2009: The first detection of ions created using a 412nm laser incident upon out strontium MOT!

19th - 23rd January 2009: The paper on spectroscopy in Clementine's cell is finished. It is called Modulation-free pump-probe spectroscopy of strontium atoms. We hope to publish it in J. Phys. B. You can find it on the ArXiv here.

12th - 16th January 2009: Some analysis of the MCP has been done, and we have been preparing to take further data for our forthcoming paper on polarization spectroscopy.

5th - 9th January 2009: LabView code has been written to extract counts from our MCP, so further analysis can take place. We are also preparing to take some spectroscopic data for our next paper...

15th - 20th December 2008: We turned on our micro channel plate (MCP), and have observed a signal. What this signal is we are yet to know, it may be Strontium ions, or dark counts.

8th - 12th December 2008: Our 412nm laser was turned on after some time in limbo. It craved attention.

1st - 5th December 2008: The MOT has been fully characterised within the limits of the current experimental set up. Temperatures as low as 2.6mK have been observed.

24th - 28th November 2008: This week I have been working real hard to get a temperature measurement of our MOT done. The answer via a "release and image" method is around 5.5mK. "Release and recapture" data has also been taken.

17th - 21st November 2008: Our CCD camera is fully integrated into our system and can image the MOT. Our locking spectroscopy has been reoptimised. Density measurements of the MOT suggest we have 108 - 109 atoms per cm3.

3rd - 14th November 2008: These two weeks were spent in Phillip Grangier's group at the Institut d'Optique in Orsay (Paris). I point you here for information on their group. I gave a presentation on the strontium project.

27th - 31st October 2008: The CCD camera is now fully calibrated, however our laser broke down, preventing further work. Our MOT behaviour was found to fit with the standard theory on the subject.

20th - 24th October 2008: This week has been spent calibrating our CCD camera, and cursing LabView's png conversion thingumy.

13th - 17th October 2008: I've been playing with LabView to bring our experiment under computer control, in particular integrating our Pixelfly CCD camera.

6th - 10th October 2008: Several atom number measurements have been made, and our observations seem to broadly agree with theory. Atom numbers of 100,000 to 10,000,000 have been measured under various conditions.

29th September - 3rd October 2008: This week I have begun characterising our Strontium MOT, as well as optimising our imaging system.

15th - 19th September 2008: Welcome to Graham, who has started his Ph.D. on the Strontium Project this week. This week I have been testing the switch for the MOT coils, been panicking slightly, and optimised our MOT imaging system.

8th - 12th September 2008: This week I built a switch for our MOT coils, and spent a few days chasing noise in our spectroscopy system.

1st - 5th September 2008: This week I have built a photodiode system to study our MOT. Also, our paper on Liz's first generation strontium vapor cell is on the arxiv here.

25th - 29nd August 2008: The task for this week was locking our 461nm laser. We managed to lock the laser with the MOT visible using a novel form of polarisation spectroscopy (paper pending!) and a home-made integrator.

18th - 22nd August 2008: This week I made this website, helped our summer student Clementine build the second version of our strontium dispenser cell (which is now pumping down), and did such glamourous tasks as cabling and laser alignment.

Content © James Millen, Durham University 2009