ultra-cold beams from ion traps Hiromi Okamoto Brooks, Stephen Dear Stephen,  We have four independent S-POD systems currently operating in my small lab here. These systems have been employed for different research themes in fundamental beam physics, so the designs of the four Paul traps are different or, in other words, optimized for their primary purposes. See the attached pdf files (S-POD I, II, III, IV) for some information about their basic design specifications. We recently resumed the laser cooling experiment in S-POD I to produce nitrogen-vacancy centers in diamond. Our new approach is based on the “ion machine gun” described in the attached paper (S-POD I.pdf). For this purpose, we only need a few nitrogen ions in every shot, sympathetically cooled through Coulomb interaction with ultracold calcium ions. According to our recent simulations, the normalized root-mean-squared emittance of ejected ions could be on the order of 10^(-16) m. The number of ions confineable in a Paul trap depends on the design of the quadrupole electrodes. If longer electrode rods are used for the ion confinement region, you can store more ions. In the S-POD II, III, and IV, it is possible to store 10 million ions within a region of several centimeters long. Note that the operating frequency of the S-POD I for laser-cooling experiment is 2 MHz, twice higher than that of other S-PODs. This makes the Paul trap more compact. As a result, the confinable ion number is reduced in the S-POD I. I would also like to call your attention to the fact that making a huge Coulomb crystal is more difficult in practice.  Another important point you might consider is the collisional heating during the ion extraction process. The heating effect could be made almost negligible in the extraction of a string Coulomb crystal. As I mentioned above, an extremely low emittance should be achievable. In the extraction of a large multi-shell Coulomb crystal, however, the attainable emittance will be worsened because the ordered crystalline structure is probably destroyed when it comes out from the trap. (Nevertheless, I think you can still expect an emittance far lower than any regular beams from any regular ion sources.) _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ Hiromi OKAMOTO Beam Physics Group Graduate School of Advanced Science and Engineering Hiroshima University 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 JAPAN TEL : +81-82-424-7032 FAX : +81-82-424-7034 _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ > 2022/12/03 4:20?Brooks, Stephen ????: > > Dear Okamoto-san, > > I saw some very interesting slides from the COOL'15 conference where you had produced a Coulomb crystal in an ion trap - and an IPAC10 paper where you extracted ultra-low emittance ions. > > I was wondering if your research on cold Coulomb crystals was still continuing? (other than S-POD, which is different) > > I've been working with some people at BNL and RAL (at the IBEX trap) about a proposal to maybe build or use an ion trap, for the purpose of extracting the beam and then bringing it to a very small focus. Even at ~MeV energies, the focus could potentially be very dense (>100g/cm^3, but only 1nm diameter) due to the near-zero emittance. > >     -Stephen Brooks, Stephen Fri 02/12/2022 14:54 Actually S-POD includes cooling, so is definitely of interest to us too. I saw a recent 2019 paper where 6 million Ca+ ions were stored. This seems a similar number to my simulations of ion traps. -Stephen Brooks, Stephen Fri 02/12/2022 14:20 Dear Okamoto-san, I saw some very interesting slides from the COOL'15 conference where you had produced a Coulomb crystal in an ion trap - and an IPAC10 paper where you extracted ultra-low emittance ions. I was wondering if your research on cold Coulomb crystals