To illustrate the coherence problems in X-ray imaging we shall examine - scanning X-ray microscopy - holography, and - soft X-ray diffraction as illustrative examples. We show that only X-rays from within the emittance xx'yy' < (2.44λ)2 have the necessary spatial coherence to yield diffraction- limited images. The degree of temporal coherence required depends on the nature of the imaging system, and the size of the specimen. In conventional X-ray systems, spatial coherence is generated by collimation, while temporal coherence is achieved with monochromators. In these systems, then, one filters out a minute coherent fraction of an intense incoherent beam. Aside from the inefficiency of the procedure, there is a practical limitation of the temporal coherence length of about 103λ that one can generate this way in the soft X-ray regime.
{"title":"Coherent Soft X-Rays in High Resolution Imaging","authors":"M. Howells, J. Kirz","doi":"10.1063/1.34649","DOIUrl":"https://doi.org/10.1063/1.34649","url":null,"abstract":"To illustrate the coherence problems in X-ray imaging we shall examine\u0000 - scanning X-ray microscopy\u0000 - holography, and\u0000 - soft X-ray diffraction\u0000 as illustrative examples. We show that only X-rays from within the emittance xx'yy' < (2.44λ)2 have the necessary spatial coherence to yield diffraction- limited images. The degree of temporal coherence required depends on the nature of the imaging system, and the size of the specimen. In conventional X-ray systems, spatial coherence is generated by collimation, while temporal coherence is achieved with monochromators. In these systems, then, one filters out a minute coherent fraction of an intense incoherent beam. Aside from the inefficiency of the procedure, there is a practical limitation of the temporal coherence length of about 103λ that one can generate this way in the soft X-ray regime.","PeriodicalId":436319,"journal":{"name":"Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123258380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An electron beam travelling through a bending magnet emits radiation in all the components of its Fourier spectrum. The emission on the harmonics depends on the bunching tightening. This emission is enhanced if the beam goes through a wiggler.
{"title":"Extreme Uv Generation with Two-Stage Free Electron Laser","authors":"I. Boscolo, W. Colson, V. Stagno","doi":"10.1063/1.34634","DOIUrl":"https://doi.org/10.1063/1.34634","url":null,"abstract":"An electron beam travelling through a bending magnet emits radiation in all the components of its Fourier spectrum. The emission on the harmonics depends on the bunching tightening. This emission is enhanced if the beam goes through a wiggler.","PeriodicalId":436319,"journal":{"name":"Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124183859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Following a discussion of the circumstances under which permanent magnets have a performance that is superior to magnets that are excited by coils (room temperature or superconducting), the properties of two specific types of linear permanent magnet undulators are described. The discussion of the performance limitations of these undulators is complemented by a description of design details to the extent necessary to appreciate the importance of some seemingly unimportant features. Effects of tolerances are clearly important and will be even more important for the very long undulators that one might build in the future. It is shown what has been done in the past, and what one may want to do in the future, to reduce the detrimental effects of tolerances. In addition to these discussions of linear undulators, a conceptual design of a helical permanent magnet undulator (with adjustable length, if desired) is shown, and the performance limitation of this device is discussed.
{"title":"New Technologies: Permanent Magnet Undulators","authors":"K. Halbach","doi":"10.1063/1.34647","DOIUrl":"https://doi.org/10.1063/1.34647","url":null,"abstract":"Following a discussion of the circumstances under which permanent magnets have a performance that is superior to magnets that are excited by coils (room temperature or superconducting), the properties of two specific types of linear permanent magnet undulators are described. The discussion of the performance limitations of these undulators is complemented by a description of design details to the extent necessary to appreciate the importance of some seemingly unimportant features. Effects of tolerances are clearly important and will be even more important for the very long undulators that one might build in the future. It is shown what has been done in the past, and what one may want to do in the future, to reduce the detrimental effects of tolerances. In addition to these discussions of linear undulators, a conceptual design of a helical permanent magnet undulator (with adjustable length, if desired) is shown, and the performance limitation of this device is discussed.","PeriodicalId":436319,"journal":{"name":"Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122830416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Ortega, C. Bazin, M. Bergher, M. Billardon, D. Deacon, P. Elleaume, G. Jézéquel, M. Velghe, Y. Petroff
The recent experiments on the F.E.L. are described. The amplification of the emission emitted by the Optical Klystron and stored in the optical cavity has been demonstrated. An amplification of the stored emission by a factor of more than 2 is reported, indicating that the gain of the Optical Klystron is very close to the cavity losses ( 90 %). Plans to increase this gain include the use of an optimised electron energy (180 MeV), the injection of the ring with positrons and the construction of an additional high frequency RF cavity. Some prospects of the F.E.L. in the visible and U.V. regions on Super A.C.O. and D.C.I. are given. It is concluded that the electron beam properties and especially the maximum attainable electronic density are very crucial if one wants to reach the V.U.V. region. The mirror behavior under the very intense optical power delivered by the undulator on various harmonics should also receive a great concern.
{"title":"Recent Undulator and F.E.L. Experiments and Prospects at Lure","authors":"J. Ortega, C. Bazin, M. Bergher, M. Billardon, D. Deacon, P. Elleaume, G. Jézéquel, M. Velghe, Y. Petroff","doi":"10.1063/1.34650","DOIUrl":"https://doi.org/10.1063/1.34650","url":null,"abstract":"The recent experiments on the F.E.L. are described. The amplification of the emission emitted by the Optical Klystron and stored in the optical cavity has been demonstrated. An amplification of the stored emission by a factor of more than 2 is reported, indicating that the gain of the Optical Klystron is very close to the cavity losses ( 90 %). Plans to increase this gain include the use of an optimised electron energy (180 MeV), the injection of the ring with positrons and the construction of an additional high frequency RF cavity. Some prospects of the F.E.L. in the visible and U.V. regions on Super A.C.O. and D.C.I. are given. It is concluded that the electron beam properties and especially the maximum attainable electronic density are very crucial if one wants to reach the V.U.V. region. The mirror behavior under the very intense optical power delivered by the undulator on various harmonics should also receive a great concern.","PeriodicalId":436319,"journal":{"name":"Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1984-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130844843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The main goal of FEL experiments, both with recirculating and non recirculating machines, is to reach a stable oscillator by adding two mirrors at the ends of the undulator to form an optical cavity. In any case, it is necessary to achieve enough gain in order to overcome losses due essentially to end mirrors absorptions.
{"title":"Free Electron Laser on Higher Harmonics","authors":"R. Barbini, G. Vignola","doi":"10.1063/1.34626","DOIUrl":"https://doi.org/10.1063/1.34626","url":null,"abstract":"The main goal of FEL experiments, both with recirculating and non recirculating machines, is to reach a stable oscillator by adding two mirrors at the ends of the undulator to form an optical cavity. In any case, it is necessary to achieve enough gain in order to overcome losses due essentially to end mirrors absorptions.","PeriodicalId":436319,"journal":{"name":"Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation","volume":"110 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1984-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124442496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An XUV free-electron laser (FEL) driven by a linear accelerator appears to be feasible for wavelengths as short as 50 nm. This projection is based upon the anticipated successful use of high peak-current (~100 A) linacs in forthcoming FEL oscillator experiments at infrared and visible wavelengths at Los Alamos and Boeing/Mathematical Sciences Northwest. As an alternative to schemes involving storage rings, a linac provides a train of individual electron bunches separated by 10-100 ns and duration of 10-30 ps. Further, electrons pass through the undulator magnet only once, but their remaining energy may be recovered in a separate decelerating structure and fed back into the primary accelerator.
{"title":"A Linac-Driven XUV Free-Electron Laser","authors":"B. Newnam, J. Goldstein, J. Fraser, R. Cooper","doi":"10.1063/1.34635","DOIUrl":"https://doi.org/10.1063/1.34635","url":null,"abstract":"An XUV free-electron laser (FEL) driven by a linear accelerator appears to be feasible for wavelengths as short as 50 nm. This projection is based upon the anticipated successful use of high peak-current (~100 A) linacs in forthcoming FEL oscillator experiments at infrared and visible wavelengths at Los Alamos and Boeing/Mathematical Sciences Northwest. As an alternative to schemes involving storage rings, a linac provides a train of individual electron bunches separated by 10-100 ns and duration of 10-30 ps. Further, electrons pass through the undulator magnet only once, but their remaining energy may be recovered in a separate decelerating structure and fed back into the primary accelerator.","PeriodicalId":436319,"journal":{"name":"Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1984-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134222229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Quantum Flucuations in Free Electron Lasers","authors":"S. Benson","doi":"10.1364/feg.1983.wa1","DOIUrl":"https://doi.org/10.1364/feg.1983.wa1","url":null,"abstract":"The effects of quantum flucuations are X-ray free electron laser performance is studied and shown to be negligible for all reasonable designs.","PeriodicalId":436319,"journal":{"name":"Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131578618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The quantum regime for a free-electron laser is defined as that in which the energy lost by an electron upon emission of a photon is larger than the homogeneous broadening due to the finite interaction time. We anticipate that soft x-ray free-electron lasers pumped by an optical wave (rather than a permanent-magnet wiggler), will operate in that regime. The small-signal gain in this regime is given by an expression which is explicitly quantum-mechanical.
{"title":"Free-Electron Lasers in the X-Ray Region: The Quantum Regime","authors":"J. Gea-Banacloche, G. Moore, M. Scully","doi":"10.1364/feg.1983.tua7","DOIUrl":"https://doi.org/10.1364/feg.1983.tua7","url":null,"abstract":"The quantum regime for a free-electron laser is defined as that in which the energy lost by an electron upon emission of a photon is larger than the homogeneous broadening due to the finite interaction time. We anticipate that soft x-ray free-electron lasers pumped by an optical wave (rather than a permanent-magnet wiggler), will operate in that regime. The small-signal gain in this regime is given by an expression which is explicitly quantum-mechanical.","PeriodicalId":436319,"journal":{"name":"Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134186268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is possible to bunch a relativistic electron beam in a storage ring using a powerful laser in conjunction with a periodic undulator magnet. Such a spatially bunched beam passing through a periodic undulator magnet radiates much more strongly than a normal unbunched beam. This optical klystron effect also generates significant harmonic output, much as in a conventional microwave klystron, only in this case, the output wavelengths are in the extreme ultraviolet (XUV). It is useful to think of the relativistic electron beam in the storage ring as a kind of non-linear medium for generating harmonics. Conversion efficiencies from laser power to harmonic output in the range 2000 Å to 100 Å vary from 10−3 down to 10−8 for a practical experiment using the National Synchrotron Light Source (NSLS) 700 MeV storage ring at Brcokhaven. This exceeds by several orders of magnitude any other technique for generating tunable coherent light in the XUV region, and will make possible a practical coherent light source for high resolution spectroscopy, microscopy, lithography, and holography. The physics of the bunching and harmonic generation process will be discussed, as well as some details of a computer simulation of the proposed NSLS Brookhaven experiment. In addition, a proposal for a tunable XUV light source based on this technique will be presented.
{"title":"Laser harmonics from 2000 Å to 100 Å","authors":"B. Kincaid, R. Freeman","doi":"10.1364/feg.1983.tua3","DOIUrl":"https://doi.org/10.1364/feg.1983.tua3","url":null,"abstract":"It is possible to bunch a relativistic electron beam in a storage ring using a powerful laser in conjunction with a periodic undulator magnet. Such a spatially bunched beam passing through a periodic undulator magnet radiates much more strongly than a normal unbunched beam. This optical klystron effect also generates significant harmonic output, much as in a conventional microwave klystron, only in this case, the output wavelengths are in the extreme ultraviolet (XUV). It is useful to think of the relativistic electron beam in the storage ring as a kind of non-linear medium for generating harmonics. Conversion efficiencies from laser power to harmonic output in the range 2000 Å to 100 Å vary from 10−3 down to 10−8 for a practical experiment using the National Synchrotron Light Source (NSLS) 700 MeV storage ring at Brcokhaven. This exceeds by several orders of magnitude any other technique for generating tunable coherent light in the XUV region, and will make possible a practical coherent light source for high resolution spectroscopy, microscopy, lithography, and holography. The physics of the bunching and harmonic generation process will be discussed, as well as some details of a computer simulation of the proposed NSLS Brookhaven experiment. In addition, a proposal for a tunable XUV light source based on this technique will be presented.","PeriodicalId":436319,"journal":{"name":"Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115982396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adequate gain appears available to operate storage ring FEL oscillators at wavelengths at least as short as 100 Å. Operation at these wavelengths will require a flat, low emittance electron beam and a long interaction region.
{"title":"General Characteristics and Requirements of XUV Storage Ring FEL's","authors":"J. Madey","doi":"10.1364/feg.1983.ma2","DOIUrl":"https://doi.org/10.1364/feg.1983.ma2","url":null,"abstract":"Adequate gain appears available to operate storage ring FEL oscillators at wavelengths at least as short as 100 Å. Operation at these wavelengths will require a flat, low emittance electron beam and a long interaction region.","PeriodicalId":436319,"journal":{"name":"Topical Meeting on Free Electron Generation of Extreme Ultraviolet Coherent Radiation","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116521393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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