Reliable atmospheric surveys for carbon distributions will be essential to building an understanding of the Earth\u27s carbon cycle and the role it plays in climate change. One of the core needs of NASA \u27s Active Sensing of CO2 Over Nights, Days and Seasons (ASCENDS) Mission is to advance the range and precision of current remote atmospheric survey techniques. The feasibility of using accelerator-based sources of infrared light to improve current airborne lidar systems has been explored. A literary review has been conducted to asses the needs of ASCENDS versus the current capabilities of modern atmospheric survey technology, and the parameters of a free electron laser (FEL) source were calculated for a lidar system that will meet these needs. By using the  Next Linear Collider  from the Stanford Linear Accelerator Center (SLAC), a mobile FEL-based lidar may be constructed for airborne surveillance. The calculated energy of the lidar pulse is 0.1 joule: this output is a two orders of magnitude gain over current lidar systems, so in principle, the mobile FEL will exceed the needs of ASCENDS. Further research will be required to asses other challenges to mobilizing the FEL technology

Johnson, S.

Koscielniak, S., (Ed.)

Krafft, Geoffrey A.

Satogata, T., (Ed.)

Schaa, V.R.W., (Ed.)

Terzić, Balša

Thomson, J., (Ed.)

English

Old Dominion University

Old Dominion University ODU Digital Commons Physics Faculty Publications Physics 2018 Mobile Free-Electron Laser for Remote Atmospheric Survey S. Johnson Old Dominion University Balša Terzić Old Dominion University, bterzic@odu.edu Geoffrey A. Krafft Old Dominion University, gkrafft@odu.edu S. Koscielniak (Ed.) T. Satogata (Ed.) See next page for additional authors Follow this and additional works at: https://digitalcommons.odu.edu/physics_fac_pubs  Part of the Engineering Physics Commons Original Publication Citation Johnson, E. S., Terzić, B., & Krafft, G. A. (2018). Mobile free-electron laser for remote atmospheric survey. In S. Koscielniak, T. Satogata, V.R.W. Schaa, J. Thomson (Eds.), Proceedings of the 9th International Particle Accelerator Conference (pp. 4351-4353). JACoW. https://doi.org/10.18429/JACoW-IPAC2018-THPMK026 This Conference Paper is brought to you for free and open access by the Physics at ODU Digital Commons. It has been accepted for inclusion in Physics Faculty Publications by an authorized administrator of ODU Digital Commons. For more information, please contact digitalcommons@odu.edu. Authors S. Johnson, Balša Terzić, Geoffrey A. Krafft, S. Koscielniak (Ed.), T. Satogata (Ed.), V.R.W. Schaa (Ed.), and J. Thomson (Ed.) This conference paper is available at ODU Digital Commons: https://digitalcommons.odu.edu/physics_fac_pubs/775 MOBILE FREE-ELECTRON LASER FOR REMOTE ATMOSPHERICSURVEYE. S. Johnson∗, B. Terzić,G. A. Krafft1, Old Dominion University, Norfolk, VA1Thomas Jefferson National Laboratory, Newport News, VAAbstractThe application of using accelerator-science to improvecurrent remote atmospheric survey techniques has been ex-plored. A literature review has been conducted to asses theneeds of NASA ’s Active Sensing of CO2 Over Nights, Daysand Seasons (ASCENDS) versus the current capabilitiesof contemporary atmospheric survey technology, and theparameters of a free electron laser (FEL) source were calcu-lated for a lidar system that will meet these needs. By usingthe “Next Linear Collider” accelerating structure from theStanford Linear Accelerator Center (SLAC) [1], a mobileFEL-based lidar may be constructed for airborne surveil-lance. The calculated energy of the lidar pulse is 0.1 joule -athree orders of magnitude gain over current lidar systems [2].Therefore in principle, the mobile FEL will exceed the needsof ASCENDS.INTRODUCTIONWe seek to assess the feasibility of applying accelerator-based sources of EM radiiation to advance the state of theart of atmospheric survey. To that purpose, we propose animprovement to airborne lidar techniques by introducing ahigher intensity, accelerator based seed laser: a mobile plat-form free electron laser (FEL). This beneficial intersectionof two previously disjoint fields of research offers promis-ing solutions to obstacles facing NASA ’s Active Sensingof CO2 Over Nights, Days and Seasons (ASCENDS) mis-sion through the implementation of well vetted acceleratortechnology.Airborne Lidar for Atmospheric SurveyAirborne lidar is a prevailing method of remote detectionof atmospheric concentrations of various molecular species.Lidar sensors emit a paired laser signal and compute targetspecies concentration by calculating the difference in ab-sorption levels and returns from the paired signal: one beamhas a wavelength matched to an absorption frequency of thetarget and the second beam is off of the absorption frequency.This difference in the two signals reflected back upon thesensor apparatus is directly proportional to the number oftarget species present in the laser column. For a pulsed li-dar signal, the time lapse between the initial pulse and thereceived signal can be resolved to determine the distancebetween the sensor and the carbon dioxide. Ultimately thedata received may be rendered to build a three dimensionaltopography of the species density in the area of surveillance.∗ egrim007@odu.eduNeeds of the NASA ASCENDS MissionThe Intergovernmental Panel on Climate Change hasconcluded that global industrialization has dramatically in-creased the production and subsequent emission into theatmosphere of carbon dioxide [3]. Increased abundance ofatmospheric carbon dioxide is understood to be the largesthuman created function for climate change [4]. The currentbackground concentration of carbon dioxide has grown toapproximately 406 ppm; historically carbon density neverexceeded 280 ppm before the industrial revolution [5]. Sincecarbon dioxide is chemically inert, it can last for hundredsof years once it has accumulated in the atmosphere [6]. Esti-mates for limiting global warming to a 2 degree centigradeincrease call for a one third reduction in these emissionswithin the next twenty years.To be useful in reducing uncertainties about carbonsources and sinks, the atmospheric carbon dioxide measure-ments need to have a high resolution with at least a 0.3%precision, or an accuracy of about 1-2 ppm. Substantialincrease to the power emitted by the laser, however, wouldsignificantly increase the signal-to-noise ratio and therebyincrease the precision of the CO2 measurement [4].The solid state lasers used in most remote lidar sourceslimit the spatial range of survey. The common practice isto take measurements from aircraft within the Earth’s at-mosphere as opposed to taking measurements from orbit-ing satellites because the range of most lidar assemblies isless than 12 kilometers. The aircraft mobility grants theresearcher an advantageous line of sight for the lidar thatis unavailable to ground based remote sensors, and this de-mand for mobility limits the size of the laser and receiverapparatus. As with radar, measurement resolution decreasesprecipitously as a square of the range. The range of the mea-surements may be extended only through substantial gainsin the laser intensity output. Ultimately, the ASCENDS mis-sion intends to conduct atmospheric surveys from orbit, sothere is a critical need for increases in the lidar signal laserpower in order to increase the range of the remote sensor to400 kilometers [7].Mobile FEL for Atmospheric SurveyThe power gains necessary to overcome the shortfalls inboth range and precision of contemporary lidar techniquesmay be achieved by abandoning the solid state lasers in favorof a compact FEL. More specifically, a high-energy FEL, orwiggler, may be implemented to provide substantial gainsin pulse intensity, and the FEL will create monochromaticinfrared pulses with the same general properties as the cur-rent leading lidar sources. Historically, a high intensity, high9th International Particle Accelerator Conference IPAC2018, Vancouver, BC, Canada JACoW PublishingISBN: 978-3-95450-184-7 doi:10.18429/JACoW-IPAC2018-THPMK02602 Photon Sources and Electron AcceleratorsA05 Synchrotron Radiation FacilitiesTHPMK0264351ContentfromthisworkmaybeusedunderthetermsoftheCCBY3.0licence(©2018).Anydistributionofthisworkmustmaintainattributiontotheauthor(s),titleofthework,publisher,andDOI.quality FEL capable of lidar operations would have been thesize of a large building [8], but advances in particle acceler-ator technologies [1] have made it possible to construct thesame powerful laser in a mobile shipping container or in thefuselage of a small jet.The scope of this work is to show that the construction ofa high-performance, mobile FEL-based lidar is possible inprinciple. Further research, specifically sensitivity tests, willbe required to identify and overcome practical considerationsfor deploying this technology. Since all of the componentsof the proposed device have already been developed and wellvetted, this avenue of research will be relatively low risk.FEASIBILITY OF A MOBILE FELTo illustrate the advantages of mobilizing FEL technol-ogy for the purpose of atmospheric survey, it will first beshown that a well-established FEL, specifically the Vander-bilt Free-Electron Laser Center [8], can generate a pulsedlaser that will exceed the current goals of ASCENDS. As apoint of reference, the feasibility of the proposed improve-ments will be compared to a highly effective pulsed lidarsystem developed by NASA Goddard Space Flight Center(GSFC) [2]. Since the FEL at Vanderbilt is much too largeto be mobilized for atmospheric survey, it will be shownhere that a similar FEL may be constructed into a compactplatform. The key to downsizing this technology lies in thepowerful, yet small accelerator structures, “The Next LinearCollider,” developed at the Stanford Linear Accelerator Cen-ter (SLAC) [1]. A prescription that is based on developed,well-vetted accelerator components for a mobile FEL plat-form will be presented. This mobile FEL will exceed therange and precision demands of the ASCENDS mission.The Current State of Atmospheric SurveyThe GSFC team has been chosen to represent the the cur-rent state of atmospheric survey because they have a decadelong track record of airborne lidar campaigns in pursuit ofthe ASCENDS mission goals. Their publication record re-flects significant improvements in lidar technology. Thisteam has executed many successful atmospheric survey mis-sion under a variety of environmental conditions [4]. Theteam has produced lidar output pulse energy at 0.475 mJ,which places their apparatus amongst the most sensitiveoperating survey lasers. Their current research involvingplanar waveguide(PWG)-based power amplifiers has mod-eled output energies in a higher order of magnitude: 6.7mJ [2]. The GSFC team’s years of experience and dedica-tion to the ongoing development of lidar technology makethem a fine representative of the current state of atmosphericsurvey technique.In order to gauge the feasibility of a FEL-based lidar, thefree-electron laser would first have to be shown to replicatethe beam quality of the solid state laser at the prescribedfrequency. Once the beam quality at the desired wavelengthhas been established, substantial increases to the laser pulseenergy will need to be illustrated in order to show meaningfulTable 1: NASA Goddard Space Flight Center Airborne LidarParameters [2] V. Vanderbilt Free-Electron Laser Center [8]..Parameter GSFC VanderbiltEmission Wavelength [nm] 1572.33 1572.33Pulse Repetition [Hz] 104 60Pulse Width [µs] 1.5 0.5-6Laser Pulse Energy [mJ] 0.475 400improvements to the range and precision of the atmosphericsurvey: specifically, the goal of ASCENDS s to produce alidar laser pulse at 3.2 mJ [2].As shown in Table(1), the pulse energy of the VanderbiltFEL far exceeds the current state of atmospheric lidar signals.Now, the task is to rebuild this accelerator-based laser sourceinto a much smaller package.Proposed Mobile FELIt would have to be shown that a FEL with this electronbeam energy demand could be constructed within a mobile,airborne platform. There are five main components neces-sary to build the FEL within the given size constraints: theelectron gun, the accelerator structure, the RF source forthe accelerator structure, the optical cavity of the wiggler,and the laser delivery apparatus. This survey does not repre-sent an exhaustive optimization of an FEL; this prescriptionserves to show it is possible, in principle, to construct a com-pact FEL with substantial energy gains over current lidarseed lasers.Table 2: ASCENDS Laser Requirements [2] v. ProposedMobile FEL.Parameter ASCENDS MFELEmission Wavelength [nm] 1572.33 1572.33Pulse Width [µs] 0.1-1 0.5 − 6Pulse Repetition [Hz] 7.5 × 103 60Average Power [W] 20 11Laser Pulse Energy [mJ] 2.5 400The Vanderbilt University Free-Electron Laser Centeruses a model FEL I built by Sierra Laser Systems that may beused to produce an equivalent laser pulse quality as that usedby the GSFC team [8]. The optical cavity, the componentwhich houses the wiggler itself, from this FEL will meet theneeds of the proposed lidar. Additionally, the Vanderbilt op-tical cavity is able to deliver the emitted radiation throughouttheir laboratory space into various tools and equipment viaan optical-beam transport system designed and constructedby Optomec Design Company. This system may be used to9th International Particle Accelerator Conference IPAC2018, Vancouver, BC, Canada JACoW PublishingISBN: 978-3-95450-184-7 doi:10.18429/JACoW-IPAC2018-THPMK026THPMK0264352ContentfromthisworkmaybeusedunderthetermsoftheCCBY3.0licence(©2018).Anydistributionofthisworkmustmaintainattributiontotheauthor(s),titleofthework,publisher,andDOI.02 Photon Sources and Electron AcceleratorsA05 Synchrotron Radiation Facilitiesfurther reduce sources of error incurred while delivering thelidar signal through the fuselage of the aircraft.The energy needs of electron beam can be met by the“Next Linear Collider" developed by SLAC at Stanford [1].These NLC structures provide stable, long term operationat very high gradient (65 MeV/m). Since our minimum re-quirement for the electron beam is 50 MeV, two of theseone meter long structures in series will provide sufficientenergy to the electron beam. This accelerator structure is thekey to making the FEL compact: older linear acceleratorswould have required tens of meters to reach these energyrequirements, but the SLAC structures require only two me-ters to meet the energy needs of the lidar. The frequency ofthe emitted laser pulse is a function of the electron energy;therefore, the tunability of the accelerator structures allowsthe laser emitted from the FEL to also be tunable. Theseaccelerator structures requires an 11.4 GHz RF source whichmay be satisfied by the X-band klystron [9].The FEL requires a high voltage dc photonemission elec-tron gun with high brightness and tight emittance, i.e. lowdeviation from the beam trajectory axis, because linear accel-erators, while having a relatively small foot print, are unableto correct electron beam quality. The high voltage electrongun from Cornell University provides an adjustable anode-cathode gap which has been proven to provide consistentemittance control under realistic breakdown conditions [10].This gun also features a segmented insulator and guard ringsto ensure proper operation even while operating at extremelyhigh voltage levels.All of these components together could be used to con-struct an FEL with a high quality, high intensity laser pulse,and this free-electron laser will have a relatively small footprint: the entire apparatus should be about 10 meters inlength and no more than 5 meters in width, as shown inFig. (1).Figure 1: Proposed compact free-electron laser.CONCLUSIONSThe signal power of airborne lidar systems may be in-creased by three orders of magnitude by mobilizing existingFEL technology. As shown in Table (2), these energy gainsfar exceed the requirements of the NASA ASCENDS mis-sion to accurately record carbon distributions in the atmo-sphere over and extended period of time. All of the compo-nents of the proposed FEL device have been developed andwell vetted, so continuing along this avenue of research willbe a relatively low risk endeavor. This research concludeswith confidence that the application of accelerator technol-ogy may indeed lead to substantial advancements in the fieldof atmospheric survey techniques. In fact, the mobile FELmay prove to be a powerful tool that advances many fieldsof research that require high intensity, narrow bandwidthemissions in the infrared red regime.REFERENCES[1] J. Wang, “R&D of accelerator structures at SLAC,” AcceleratorSymposium of China, vol. 9, 2005.[2] A. W. Yu et al., “Laser amplifier development for IPDA Lidarmeasurements of CO2 from space,” Proc. SPIE 9342, p. 9342,2015.[3] J. L. Verkerke, D. J. Williams, and E. Thoma, “Remote sens-ing of CO2 leakage from geological sequestration projects,”International Journal of Applied Earth Observation and Geoin-formation 31, pp. 67–77, 2014.[4] J. B. Abshire et al., “Pulsed airborne lidar measurements ofatmospheric CO2 column absorption,” Tellus B 62, no. 5, pp.770–783, 2010.[5] S.C.H. Shaftel and R. Jackson, “Global climate change: Vitalsigns of the planet,” 2018.[6] M. Reuter et al., “On the potential of the 2041- 2047 nmspectral region for remote sensing of atmospheric CO2 isotopo-logues,” Journal of Quantitative Spectroscopy and RadiativeTransfer, 113, pp. 2009–2017, Nov. 2012.[7] . NASA, “Science mission definition study & workshop,” AS-CENDS, 2015.[8] C. Brau, “The Vanderbilt university free-electron laser center,”NIM:A 319, no. 1, pp. 47-50, 1992.[9] F. Peauger et al., “A 12 GHz RF power source for the CLICstudy,” in Proc. of IPAC’10, Kyoto, Japan, 2010, paper TH-PEB053, p. 3990.[10] J. Maxson et al., “Design, conditioning, and performanceof a high voltage, high brightness Dc photoelectron gun withvariable gap,” Rev. Sci. Instr 85, p. 093306, 2014.9th International Particle Accelerator Conference IPAC2018, Vancouver, BC, Canada JACoW PublishingISBN: 978-3-95450-184-7 doi:10.18429/JACoW-IPAC2018-THPMK02602 Photon Sources and Electron AcceleratorsA05 Synchrotron Radiation FacilitiesTHPMK0264353ContentfromthisworkmaybeusedunderthetermsoftheCCBY3.0licence(©2018).Anydistributionofthisworkmustmaintainattributiontotheauthor(s),titleofthework,publisher,andDOI.-----

Mobile Free-Electron Laser for Remote Atmospheric Survey

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Mobile Free-Electron Laser for Remote Atmospheric Survey

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