Re: [ccp4bb] Femtosecond Electron Beam
Jacob We should not be comparing the Xray and electron beam fluxes in terms of particle density as the scattering cross sections are very different. I have to admit I did not see the number you are quoting, which is very low. One needs 20-30 electrons per A^2 to acheive 3A resolution. Presumably the beam can be focused to this density at the specimen plane, but I do not know for sure. Fabrizio Carbone has just sent me his latest estimates for the numbers we are discussing. But let's do as Colin suggested and discuss this further off the board and post a summary later. Cheers, Petr Sent from my iPhone On 15 Apr 2011, at 03:40, "Jacob Keller" wrote: > One of the figures they cite is 2.5 electrons per um^2, which I think > means once the whole bunch has gone through. That struck me as being > pretty far from where one needs to be to get structures. Do you know > off hand a comparable figure for the FEL experiment? I assume it would > be many orders of magnitude greater. For example, how many total > photons were in each bunch with the FEL? > > JPK > > On Thu, Apr 14, 2011 at 5:24 PM, Colin Nave > wrote: >> Petr >> Well, not sure - are we doing imaging or diffraction/scattering? >> What energy are the electrons in these sources? The idea of pulsed >> sources is to put more electrons/A^2 and still beat radiation >> damage. Can one do this when there are only around 10^6 electrons >> in perhaps a rather divergent beam? >> Shall we discuss off line (with Jacob) and present our conclusions >> when/if we get agreement? >> Regards >> Colin >> >> >> >>> -Original Message- >>> From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf >>> Of >>> Petr Leiman >>> Sent: 14 April 2011 22:59 >>> To: CCP4BB@JISCMAIL.AC.UK >>> Subject: Re: [ccp4bb] Femtosecond Electron Beam >>> >>> Colin, >>> >>> We know that with a dose of 20-30 electrons per A^2, a lot of image >>> processing, and insane amount of luck, one can reconstruct cryoEM >>> images to 3 A resolution or better. A typical protein molecule is >>> say >>> 100 A in diameter, which is ~8000 A^2 in projection. So, in an ideal >>> case one needs only 240,000 electrons to record an image of a >>> protein >>> molecule with a signal extending to 3A resolution. >>> >>> Jacob, >>> >>> Yes, you are correct. Jom et al. manipulate electron bunches of 1+ >>> Mln >>> electrons, which should be enough to record an image of a protein >>> molecule. >>> >>> Best, >>> >>> Petr >>> >>> >>> On Apr 14, 2011, at 11:13 PM, Colin Nave wrote: >>> >>>> Petr >>>> Yes, I saw the figure. Similar ones appear in the Hastings et. al. >>> paper (the SLAC one I referenced). They use a much higher energy >>> beam >>> to get the short pulse length. >>>> >>>> I still believe the issues are >>>> >>>> 1. For diffraction, can you get a low enough electron beam >>>> divergence >>> to resolve larger unit cells? The peaks appear rather broad in the >>> foil >>> experiments. Luiten et. al. believe they can extend the technique to >>> resolve cells of a few tens of nm which would be fine. Their ideas >>> for >>> doing this appear to be quite novel. I don't know if they have >>> demonstrated this though. >>>> 2. Given the above, will there be enough electrons in one of the >>> short pulses to get enough statistics for a biological molecule or >>> protein nano-crystal? I have not seen calculations for this for >>> electron beams (as has been done for the FEL x-ray beams). >>> Actually it >>> should be quite easy to do as the cross sections are all available. >>>> 3. For imaging (i.e. using an objective lens) is the blurring I >>> mention going to be a fundamental limitation and what will this >>> limitation be? >>>> >>>> These instruments would be useful for material science applications >>> and fast chemistry investigations where some of the above issues >>> would >>> not be relevant. Not sure for imaging biological molecules. We will >>> see. >>>> >>>> Finally saying Phys Rev Let is not a high impact journal would >>> probably upset my physicist colleagues - that's fine though! >>>> >>>> Regards >>>> Colin >>>> &g
Re: [ccp4bb] Femtosecond Electron Beam
One of the figures they cite is 2.5 electrons per um^2, which I think means once the whole bunch has gone through. That struck me as being pretty far from where one needs to be to get structures. Do you know off hand a comparable figure for the FEL experiment? I assume it would be many orders of magnitude greater. For example, how many total photons were in each bunch with the FEL? JPK On Thu, Apr 14, 2011 at 5:24 PM, Colin Nave wrote: > Petr > Well, not sure - are we doing imaging or diffraction/scattering? What energy > are the electrons in these sources? The idea of pulsed sources is to put more > electrons/A^2 and still beat radiation damage. Can one do this when there are > only around 10^6 electrons in perhaps a rather divergent beam? > Shall we discuss off line (with Jacob) and present our conclusions when/if we > get agreement? > Regards > Colin > > > >> -Original Message- >> From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of >> Petr Leiman >> Sent: 14 April 2011 22:59 >> To: CCP4BB@JISCMAIL.AC.UK >> Subject: Re: [ccp4bb] Femtosecond Electron Beam >> >> Colin, >> >> We know that with a dose of 20-30 electrons per A^2, a lot of image >> processing, and insane amount of luck, one can reconstruct cryoEM >> images to 3 A resolution or better. A typical protein molecule is say >> 100 A in diameter, which is ~8000 A^2 in projection. So, in an ideal >> case one needs only 240,000 electrons to record an image of a protein >> molecule with a signal extending to 3A resolution. >> >> Jacob, >> >> Yes, you are correct. Jom et al. manipulate electron bunches of 1+ Mln >> electrons, which should be enough to record an image of a protein >> molecule. >> >> Best, >> >> Petr >> >> >> On Apr 14, 2011, at 11:13 PM, Colin Nave wrote: >> >> > Petr >> > Yes, I saw the figure. Similar ones appear in the Hastings et. al. >> paper (the SLAC one I referenced). They use a much higher energy beam >> to get the short pulse length. >> > >> > I still believe the issues are >> > >> > 1. For diffraction, can you get a low enough electron beam divergence >> to resolve larger unit cells? The peaks appear rather broad in the foil >> experiments. Luiten et. al. believe they can extend the technique to >> resolve cells of a few tens of nm which would be fine. Their ideas for >> doing this appear to be quite novel. I don't know if they have >> demonstrated this though. >> > 2. Given the above, will there be enough electrons in one of the >> short pulses to get enough statistics for a biological molecule or >> protein nano-crystal? I have not seen calculations for this for >> electron beams (as has been done for the FEL x-ray beams). Actually it >> should be quite easy to do as the cross sections are all available. >> > 3. For imaging (i.e. using an objective lens) is the blurring I >> mention going to be a fundamental limitation and what will this >> limitation be? >> > >> > These instruments would be useful for material science applications >> and fast chemistry investigations where some of the above issues would >> not be relevant. Not sure for imaging biological molecules. We will >> see. >> > >> > Finally saying Phys Rev Let is not a high impact journal would >> probably upset my physicist colleagues - that's fine though! >> > >> > Regards >> > Colin >> > >> >> -Original Message- >> >> From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf >> Of >> >> Petr Leiman >> >> Sent: 14 April 2011 21:07 >> >> To: CCP4BB@JISCMAIL.AC.UK >> >> Subject: Re: [ccp4bb] Femtosecond Electron Beam >> >> >> >> 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: >> >> >> >>>
Re: [ccp4bb] Femtosecond Electron Beam
Petr Well, not sure - are we doing imaging or diffraction/scattering? What energy are the electrons in these sources? The idea of pulsed sources is to put more electrons/A^2 and still beat radiation damage. Can one do this when there are only around 10^6 electrons in perhaps a rather divergent beam? Shall we discuss off line (with Jacob) and present our conclusions when/if we get agreement? Regards Colin > -Original Message- > From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of > Petr Leiman > Sent: 14 April 2011 22:59 > To: CCP4BB@JISCMAIL.AC.UK > Subject: Re: [ccp4bb] Femtosecond Electron Beam > > Colin, > > We know that with a dose of 20-30 electrons per A^2, a lot of image > processing, and insane amount of luck, one can reconstruct cryoEM > images to 3 A resolution or better. A typical protein molecule is say > 100 A in diameter, which is ~8000 A^2 in projection. So, in an ideal > case one needs only 240,000 electrons to record an image of a protein > molecule with a signal extending to 3A resolution. > > Jacob, > > Yes, you are correct. Jom et al. manipulate electron bunches of 1+ Mln > electrons, which should be enough to record an image of a protein > molecule. > > Best, > > Petr > > > On Apr 14, 2011, at 11:13 PM, Colin Nave wrote: > > > Petr > > Yes, I saw the figure. Similar ones appear in the Hastings et. al. > paper (the SLAC one I referenced). They use a much higher energy beam > to get the short pulse length. > > > > I still believe the issues are > > > > 1. For diffraction, can you get a low enough electron beam divergence > to resolve larger unit cells? The peaks appear rather broad in the foil > experiments. Luiten et. al. believe they can extend the technique to > resolve cells of a few tens of nm which would be fine. Their ideas for > doing this appear to be quite novel. I don't know if they have > demonstrated this though. > > 2. Given the above, will there be enough electrons in one of the > short pulses to get enough statistics for a biological molecule or > protein nano-crystal? I have not seen calculations for this for > electron beams (as has been done for the FEL x-ray beams). Actually it > should be quite easy to do as the cross sections are all available. > > 3. For imaging (i.e. using an objective lens) is the blurring I > mention going to be a fundamental limitation and what will this > limitation be? > > > > These instruments would be useful for material science applications > and fast chemistry investigations where some of the above issues would > not be relevant. Not sure for imaging biological molecules. We will > see. > > > > Finally saying Phys Rev Let is not a high impact journal would > probably upset my physicist colleagues - that's fine though! > > > > Regards > > Colin > > > >> -Original Message- > >> From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf > Of > >> Petr Leiman > >> Sent: 14 April 2011 21:07 > >> To: CCP4BB@JISCMAIL.AC.UK > >> Subject: Re: [ccp4bb] Femtosecond Electron Beam > >> > >> 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
Re: [ccp4bb] Femtosecond Electron Beam
Colin, We know that with a dose of 20-30 electrons per A^2, a lot of image processing, and insane amount of luck, one can reconstruct cryoEM images to 3 A resolution or better. A typical protein molecule is say 100 A in diameter, which is ~8000 A^2 in projection. So, in an ideal case one needs only 240,000 electrons to record an image of a protein molecule with a signal extending to 3A resolution. Jacob, Yes, you are correct. Jom et al. manipulate electron bunches of 1+ Mln electrons, which should be enough to record an image of a protein molecule. Best, Petr On Apr 14, 2011, at 11:13 PM, Colin Nave wrote: > Petr > Yes, I saw the figure. Similar ones appear in the Hastings et. al. paper (the > SLAC one I referenced). They use a much higher energy beam to get the short > pulse length. > > I still believe the issues are > > 1. For diffraction, can you get a low enough electron beam divergence to > resolve larger unit cells? The peaks appear rather broad in the foil > experiments. Luiten et. al. believe they can extend the technique to resolve > cells of a few tens of nm which would be fine. Their ideas for doing this > appear to be quite novel. I don't know if they have demonstrated this though. > 2. Given the above, will there be enough electrons in one of the short pulses > to get enough statistics for a biological molecule or protein nano-crystal? I > have not seen calculations for this for electron beams (as has been done for > the FEL x-ray beams). Actually it should be quite easy to do as the cross > sections are all available. > 3. For imaging (i.e. using an objective lens) is the blurring I mention going > to be a fundamental limitation and what will this limitation be? > > These instruments would be useful for material science applications and fast > chemistry investigations where some of the above issues would not be > relevant. Not sure for imaging biological molecules. We will see. > > Finally saying Phys Rev Let is not a high impact journal would probably upset > my physicist colleagues - that's fine though! > > Regards > Colin > >> -Original Message- >> From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of >> Petr Leiman >> Sent: 14 April 2011 21:07 >> To: CCP4BB@JISCMAIL.AC.UK >> Subject: Re: [ccp4bb] Femtosecond Electron Beam >> >> 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 >
Re: [ccp4bb] Femtosecond Electron Beam
Petr Yes, I saw the figure. Similar ones appear in the Hastings et. al. paper (the SLAC one I referenced). They use a much higher energy beam to get the short pulse length. I still believe the issues are 1. For diffraction, can you get a low enough electron beam divergence to resolve larger unit cells? The peaks appear rather broad in the foil experiments. Luiten et. al. believe they can extend the technique to resolve cells of a few tens of nm which would be fine. Their ideas for doing this appear to be quite novel. I don't know if they have demonstrated this though. 2. Given the above, will there be enough electrons in one of the short pulses to get enough statistics for a biological molecule or protein nano-crystal? I have not seen calculations for this for electron beams (as has been done for the FEL x-ray beams). Actually it should be quite easy to do as the cross sections are all available. 3. For imaging (i.e. using an objective lens) is the blurring I mention going to be a fundamental limitation and what will this limitation be? These instruments would be useful for material science applications and fast chemistry investigations where some of the above issues would not be relevant. Not sure for imaging biological molecules. We will see. Finally saying Phys Rev Let is not a high impact journal would probably upset my physicist colleagues - that's fine though! Regards Colin > -Original Message- > From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of > Petr Leiman > Sent: 14 April 2011 21:07 > To: CCP4BB@JISCMAIL.AC.UK > Subject: Re: [ccp4bb] Femtosecond Electron Beam > > 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 > &
Re: [ccp4bb] Femtosecond Electron Beam
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 >>> ***
Re: [ccp4bb] Femtosecond Electron Beam
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 > > ***
Re: [ccp4bb] Femtosecond Electron Beam
Dear Jacob, Ahmed Zewail's papers are worth consulting on this, although not protein/bio. See also the book by Zewail and Thomas, recently published, easily findable on amazon etc, as a handy overview. Best wishes, John Prof John R Helliwell DSc On 14 Apr 2011, at 14:38, Jacob Keller wrote: > 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 > ***
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 > ***
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 > ***
[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 ***
