People are looking into how to fit the old retired MeV microscopes with pulsed electron guns (problem is there are very few of those beasts left). If this works, such a machine will produce equivalent results to FEL but at a fraction of the cost.
The group at Eindhoven, which Colin had mentioned, has already made a significant progress in achieving both time and spatial coherence. They are able to manipulate electrons in ultrashort electron bunches akin to spins in an NMR machine: http://prl.aps.org/abstract/PRL/v105/i26/e264801 http://jap.aip.org/resource/1/japiau/v109/i3/p033302_s1 And this is due to the fact that electrons can be focused with lenses. Amazing stuff. We will hear more about this for sure. Sincerely, Petr ________________________________________ From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Colin Nave [colin.n...@diamond.ac.uk] Sent: Thursday, April 14, 2011 16:50 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Jacob Very good question. People are considering this sort of thing. See for example http://www-spires.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-12162.pdf Due to coulomb explosion one normally needs MeV beams to get the short bunch length. MeV beams also give a more reasonable penetration depth (not relevant for single molecules). I think the problem is that the divergence is too high to resolve diffraction spots from protein crystals (or in other words insufficient coherence). Probably fine for many small molecule crystals though. You mentioned single molecules, presumably protein molecules and I think the same would apply if trying to observe the scattering. One could try imaging (i.e. with an electron lens) rather than do diffraction. I presume this is what you mean by "focussed to solve the phase problem". However, I understand that there are problems with this as well for MeV beams but I can't remember the exact details. Can look it up if you are interested. There could of course be technical advances which would make some of these ideas possible. I think a group at Eindhoven have plans to get round some of the problems. Again I would have to look up the details. Regards Colin > -----Original Message----- > From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of > Jacob Keller > Sent: 14 April 2011 14:39 > To: CCP4BB@JISCMAIL.AC.UK > Subject: [ccp4bb] Femtosecond Electron Beam > > Dear Crystallographers, > > is there any reason why we are not considering using super-intense > femtosecond electron bursts, instead of photons? Since the scattering > of electrons is much more efficient, and because they can be focussed > to solve the phase problem, it seems that it might be worthwhile to > explore that route of single-molecule structure solution by using > electrospray techniques similar to the recently-reported results using > the FEL. Is there some technical limitation which would hinder this > possibility? > > JPK > > -- > ******************************************* > Jacob Pearson Keller > Northwestern University > Medical Scientist Training Program > cel: 773.608.9185 > email: j-kell...@northwestern.edu > *******************************************
