Dear Colin and all interested in the FEL development. Please look at the figures in the first link I mentioned. Jom Luiten et al. are able to record a 1.25 A resolution diffraction pattern of a gold foil using a pulse compressed to 50 fs. Ahmed Zewail is a pioneer of the technique but as far as I know his instrumentation is nowhere near Jom's amazing machine.
Why Jom's paper was not published in one of the high profile journals, ahem, magazines, is a mystery to me. Petr On Apr 14, 2011, at 9:11 PM, Colin Nave wrote: > Petr has provided the Eindhoven links. > > For more details on fast electron imaging (as opposed to diffraction) see > https://e-reports-ext.llnl.gov/pdf/343044.pdf > > Apparently stochastic scattering of the electrons at the high current > densities necessary for short pulsed sources result in blurring in the > image. The paper says that 10nm spatial and 10ps temporal resolution could be > achieved with 5MeV electrons and annular dark field imaging. > > Of course more recent developments at Eindhoven and elsewhere might get round > some of the limitations. > > > Colin > >> -----Original Message----- >> From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of >> Petr Leiman >> Sent: 14 April 2011 16:23 >> To: CCP4BB@JISCMAIL.AC.UK >> Subject: Re: [ccp4bb] Femtosecond Electron Beam >> >> 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 >>> *******************************************
