Author: Karkare, S.S.
Paper Title Page
MOYE6 Spin-Polarized Electron Photoemission and Detection Studies 26
 
  • A.C. Rodriguez Alicea, R. Palai
    University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico
  • O. Chubenko, S.S. Karkare
    Arizona State University, Tempe, USA
  • L. Cultrera
    BNL, Upton, New York, USA
 
  Funding: Brookhaven National Laboratory and the Department of Energy of United States under contract No. DE-SC0012704 Also, the Center for Bright Beams, NSF award PHY-1549132.
The ex­per­i­men­tal in­ves­ti­ga­tion of new pho­to­cath­ode ma- teri­als is time-con­sum­ing, ex­pen­sive, and dif­fi­cult to ac­com- plish. Com­pu­ta­tional mod­el­ling of­fers fast and in­ex­pen­sive ways to ex­plore new ma­te­ri­als, and op­er­at­ing con­di­tions, that could po­ten­tially en­hance the ef­fi­ciency of po­lar­ized elec­tron beam pho­to­cath­odes. We re­port on Monte-Carlo sim­u­la­tion of elec­tron spin po­lar­iza­tion (ESP) and quan­tum ef­fi­ciency (QE) of bulk GaAs at 2, 77, and 300 K using the data ob­tained from Den­sity Func­tional The­ory (DFT) cal- cu­la­tions at the cor­re­spond­ing tem­per­a­tures. The sim­u­lated re­sults of ESP and QE were com­pared with re­ported ex­per- imen­tal mea­sure­ments, and showed good agree­ment at 77 and 300 K.
 
slides icon Slides MOYE6 [6.235 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOYE6  
About • Received ※ 03 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 04 September 2022
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MOPA50 Integrated Photonics Structure Cathodes for Longitudinally Shaped Bunch Trains 160
 
  • S.J. Coleman, D.T. Abell, C.C. Hall
    RadiaSoft LLC, Boulder, Colorado, USA
  • R. Kapadia
    University of Southern California, Los Angeles, California, USA
  • S.S. Karkare
    Arizona State University, Tempe, USA
  • S.Y. Kim, P. Piot, J.F. Power
    ANL, Lemont, Illinois, USA
 
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DOE DE-SC0021681
Com­pact, high-gra­di­ent struc­ture wake­field ac­cel­er­a­tors can op­er­ate at im­proved ef­fi­ciency using shaped elec­tron beams, such as a high trans­former ratio beam shape, to drive the wakes. These shapes have gen­er­ally come from a pho­to­cath­ode gun fol­lowed by a trans­verse mask to im­print a de­sired shape on the trans­verse dis­tri­b­u­tion, and then an emit­tance ex­changer (EEX) to con­vert that trans­verse shape into a lon­gi­tu­di­nal dis­tri­b­u­tion. This process dis­cards some large frac­tion of the beam, lim­it­ing wall-plug ef­fi­ciency as well as leav­ing a solid ob­ject in the path of the beam. In this paper, we pre­sent a pro­posed method of using in­te­grated pho­ton­ics struc­tures to con­trol the emis­sion pat­tern on the cath­ode sur­face. This trans­verse pat­tern is then con­verted into a lon­gi­tu­di­nal pat­tern at the end of an EEX. This re­moves the need for the mask, pre­serv­ing the total charge pro­duced at the cath­ode sur­face. We pre­sent sim­u­la­tions of an ex­per­i­men­tal set-up to demon­strate this con­cept at the Ar­gonne Wake­field Ac­cel­er­a­tor.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA50  
About • Received ※ 03 August 2022 — Revised ※ 05 August 2022 — Accepted ※ 26 August 2022 — Issue date ※ 03 October 2022
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TUYD3 The Quest for the Perfect Cathode 281
 
  • J.W. Lewellen, J. Smedley, T. Vecchione
    SLAC, Menlo Park, California, USA
  • D. Filippetto
    LBNL, Berkeley, California, USA
  • S.S. Karkare
    Arizona State University, Tempe, USA
  • J.M. Maxson
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • P. Musumeci
    UCLA, Los Angeles, California, USA
 
  Funding: U.S. Department of Energy.
The next gen­er­a­tion of free elec­tron lasers will be the first to see the per­for­mance of the laser strongly de­pen­dent on the ma­te­ri­als prop­er­ties of the pho­to­cath­ode. A new in­jec­tor pro­posed for the LCLS-II HE is an ex­am­ple of this rev­o­lu­tion, with the goal of in­creas­ing the pho­ton en­ergy achiev­able by LCLS-II to over 20 keV. We must now ask, what is the op­ti­mal cath­ode, tem­per­a­ture, and laser com­bi­na­tion to en­able this in­jec­tor? There are many com­pet­ing re­quire­ments. The cath­ode must be ro­bust enough to op­er­ate in a su­per­con­duct­ing in­jec­tor, and must not cause con­t­a­m­i­na­tion of the in­jec­tor. It must achieve suf­fi­cient charge at high rep­e­ti­tion rate, while min­i­miz­ing the emit­tance. The wave­length cho­sen must min­i­mize mean trans­verse en­ergy while main­tain­ing tol­er­a­ble lev­els of multi-pho­ton emis­sion. The cath­ode must be ca­pa­ble of op­er­at­ing at high (~30 MV/m) gra­di­ent, which puts lim­its on both sur­face rough­ness and field emis­sion. This pre­sen­ta­tion will dis­cuss the trade space for such a cath­ode/laser com­bi­na­tion, and de­tail a new col­lab­o­ra­tive pro­gram among a va­ri­ety of in­sti­tu­tions to in­ves­ti­gate it.
 
slides icon Slides TUYD3 [1.632 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUYD3  
About • Received ※ 02 August 2022 — Revised ※ 04 August 2022 — Accepted ※ 14 August 2022 — Issue date ※ 26 September 2022
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TUYD4 Towards High Brightness from Plasmon-Enhanced Photoemitters 285
 
  • C.M. Pierce, I.V. Bazarov, J.M. Maxson
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • D.B. Durham, D. Filippetto, F. Riminucci
    LBNL, Berkeley, California, USA
  • A.H. Kachwala, S.S. Karkare
    Arizona State University, Tempe, USA
  • A. Minor
    UC Berkeley, Berkeley, California, USA
 
  Funding: This work is supported by DOE BES Contract No. DE-AC02-05CH11231. C.P. acknowledges NSF Award PHY-1549132 (CBB) and the US DOE SCGSR program. DD was supported by NSF Grant No. DMR-1548924 (STROBE).
Plas­monic cath­odes, whose nanoscale fea­tures may lo­cally en­hance op­ti­cal en­ergy from the dri­ving laser trapped at the vac­uum in­ter­face, have emerged as a promis­ing tech­nol­ogy for im­prov­ing the bright­ness of metal cath­odes. A six or­ders of mag­ni­tude im­prove­ment [1] in the non-lin­ear yield of met­als has been ex­per­i­men­tally demon­strated through this type of nanopat­tern­ing. Fur­ther, nanoscale lens struc­tures may focus light below its free-space wave­length of­fer­ing mul­ti­pho­ton pho­toe­mis­sion from a re­gion near 10 times smaller [2] than that achiev­able in typ­i­cal pho­toin­jec­tors. In this pro­ceed­ing, we re­port on our ef­forts to char­ac­ter­ize the bright­ness of two plas­monic cath­ode con­cepts: a spi­ral lens and a nanogroove array. We demon­strate an abil­ity to en­gi­neer and fab­ri­cate nanoscale pat­terned cath­odes by com­par­ing their op­ti­cal prop­er­ties with those com­puted with a fi­nite dif­fer­ence time do­main (FDTD) code. The emit­tance and non­lin­ear yield of the cath­odes are mea­sured under ul­tra­fast laser ir­ra­di­a­tion. Fi­nally, prospects of this tech­nol­ogy for the con­trol and ac­cel­er­a­tion of charged par­ti­cle beams are dis­cussed.
[1] Polyakov, A., et al. (2013). Physical Review Letters, 110(7), 076802.
[2] Durham, D. B., et al. (2019). Physical Review Applied, 12(5), 054057.
 
slides icon Slides TUYD4 [7.160 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUYD4  
About • Received ※ 05 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 13 September 2022
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TUYD5 Epitaxial Alkali-Antimonide Photocathodes on Lattice-matched Substrates 289
 
  • P. Saha, S.S. Karkare
    Arizona State University, Tempe, USA
  • E. Echeverria, A. Galdi, J.M. Maxson, C.A. Pennington
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • E.J. Montgomery, S. Poddar
    Euclid Beamlabs, Bolingbrook, USA
 
  Al­kali-an­ti­monides pho­to­cath­odes, char­ac­ter­ized by high quan­tum ef­fi­ciency (QE) and low mean trans­verse en­ergy (MTE) in the vis­i­ble range of spec­trum, are ex­cel­lent can­di­dates for elec­tron sources to drive X-ray Free Elec­tron Lasers (XFEL) and Ul­tra­fast Elec­tron Dif­frac­tion (UED). A key fig­ure of merit for these ap­pli­ca­tions is the elec­tron beam bright­ness, which is in­versely pro­por­tional to MTE. MTE can be lim­ited by nanoscale sur­face rough­ness. Re­cently, we have demon­strated phys­i­cally and chem­i­cally smooth Cs3Sb cath­odes on Stron­tium Ti­tanate (STO) sub­strates grown via co-de­po­si­tion tech­nique. Such flat cath­odes could re­sult from a more or­dered growth. In this paper, we pre­sent RHEED data of co-de­posited Cs3Sb cath­odes on STO. Ef­forts to achieve epi­tax­ial growth of Cs3Sb on STO are then demon­strated via RHEED. We find that films grown epi­tax­i­ally on sub­strates like STO and SiC (pre­vi­ously used to achieve sin­gle crys­talline Cs3Sb) ex­hibit QE higher than the poly­crys­talline Cs3Sb cath­odes, by an order of mag­ni­tude below pho­toe­mis­sion thresh­old. Given the larger QE, lower laser flu­ence could be used to ex­tract high charge den­si­ties, thereby lead­ing to en­hanced beam bright­ness.  
slides icon Slides TUYD5 [2.088 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUYD5  
About • Received ※ 01 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 07 September 2022
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TUYD6 Design of a 200 kV DC Cryocooled Photoemission Gun for Photocathode Investigations 292
 
  • G.S. Gevorkyan, T.J. Hanks, A.H. Kachwala, S.S. Karkare, C.J. Knill, C.A. Sarabia Cardenas
    Arizona State University, Tempe, USA
 
  Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams, and the DOE under Grant No. DE-SC0021092.
We pre­sent the first re­sults of the com­mis­sion­ing of the 200 kV DC elec­tron gun with a cryo­geni­cally cooled cath­ode at Ari­zona State Uni­ver­sity. The gun is specif­i­cally de­signed for study­ing a wide va­ri­ety of novel cath­ode ma­te­ri­als in­clud­ing sin­gle crys­talline and epi­tax­i­ally grown ma­te­ri­als at 30 K tem­per­a­tures to ob­tain the low­est pos­si­ble in­trin­sic emit­tance of UED and XFEL ap­pli­ca­tions [1]. We will pre­sent the mea­sure­ments of the cryo­genic per­for­mance of the gun and the first high volt­age com­mis­sion­ing re­sults.
[1] G. S. Gevorkyan et. al., Proc. of NAPAC19 MOPLM16 (2019)
 
slides icon Slides TUYD6 [12.632 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUYD6  
About • Received ※ 03 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 29 September 2022
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TUPA86 Simulations of Nanoblade Cathode Emissions with Image Charge Trapping for Yield and Brightness Analyses 535
 
  • J.I. Mann, G.E. Lawler, J.B. Rosenzweig, B. Wang
    UCLA, Los Angeles, California, USA
  • T. Arias, J.K. Nangoi
    Cornell University, Ithaca, New York, USA
  • S.S. Karkare
    Arizona State University, Tempe, USA
 
  Funding: National Science Foundation Grant No. PHY-1549132
Laser-in­duced field emis­sion from nanos­truc­tures as a means to cre­ate high bright­ness elec­tron beams has been a con­tin­u­ally grow­ing topic of study. Ex­per­i­ments using nanoblade emit­ters have achieved peak fields up­wards of 40 GV/m ac­cord­ing to semi-clas­si­cal analy­ses, beg­ging fur­ther the­o­ret­i­cal in­ves­ti­ga­tion. A re­cent paper has pro­vided an­a­lyt­i­cal re­duc­tions of the com­mon semi-in­fi­nite Jel­lium sys­tem for pulsed in­ci­dent lasers. We uti­lize these re­sults to fur­ther un­der­stand the physics un­der­ly­ing elec­tron rescat­ter­ing-type emis­sions. We nu­mer­i­cally eval­u­ate this an­a­lyt­i­cal so­lu­tion to ef­fi­ciently pro­duce spec­tra and yield curves. The ef­fect of space-charge trap­ping at emis­sion may be sim­ply in­cluded by di­rectly mod­i­fy­ing these spec­tra. Ad­di­tion­ally, we use a self-con­sis­tent 1-D time-de­pen­dent Schrödinger equa­tion with an image charge po­ten­tial to study the same sys­tem as a more exact, but com­pu­ta­tion­ally costly, ap­proach. With these re­sults we may fi­nally in­ves­ti­gate the mean trans­verse en­ergy and beam bright­ness at the cath­ode in these ex­treme regimes.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA86  
About • Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 03 September 2022
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WEPA65 On-Chip Photonics Integrated Photocathodes 773
 
  • A.H. Kachwala, O. Chubenko, S.S. Karkare
    Arizona State University, Tempe, USA
  • R. Ahsan
    USC, Los Angeles, California, USA
  • H.U. Chae, R. Kapadia
    University of Southern California, Los Angeles, California, USA
 
  Funding: This work is supported by the NSF Center for Bright Beams under award PHY-1549132, and by the Department of Energy, Office of Science under awards DE-SC0021092, and DE-SC0021213.
Pho­ton­ics in­te­grated pho­to­cath­odes can re­sult in ad­vanced elec­tron sources for var­i­ous ac­cel­er­a­tor ap­pli­ca­tions. In such pho­to­cath­odes, light can be di­rected using wave­guides and other pho­tonic com­po­nents on the sub­strate un­der­neath a pho­toe­mis­sive film to gen­er­ate elec­tron emis­sion from spe­cific lo­ca­tions at sub-mi­cron scales and at spe­cific times at 100-fem­tosec­ond scales along with trig­ger­ing novel pho­toe­mis­sion mech­a­nisms re­sult­ing in brighter elec­tron beams and en­abling un­prece­dented spa­tio-tem­po­ral shap­ing of the emit­ted elec­trons. In this work we have demon­strated pho­toe­mis­sion con­fined in the trans­verse di­rec­tion using a nanofab­ri­cated Si3N4 wave­guide un­der­neath a 40-nm thick ce­si­ated GaAs pho­toe­mis­sive film, thus demon­strat­ing a proof of prin­ci­ple fea­si­bil­ity of such pho­ton­ics in­te­grated pho­to­cath­odes. This work paves the way to in­te­grate the ad­vances in the field of pho­ton­ics and nanofab­ri­ca­tion with pho­to­cath­odes to de­velop bet­ter elec­tron sources.
 
poster icon Poster WEPA65 [0.642 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA65  
About • Received ※ 26 July 2022 — Revised ※ 06 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 10 August 2022
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WEPA66 Near-Threshold Photoemission from Graphene Coated Cu Single Crystals 776
 
  • C.J. Knill, S.S. Karkare
    Arizona State University, Tempe, USA
  • H. Ago, K. Kawahara
    Global Innovation Center, Kyushu University, Kasuga, Fukuoka, Japan
  • E. Batista, N.A. Moody, G.X. Wang, H. Yamaguchi, P. Yang
    LANL, Los Alamos, New Mexico, USA
 
  Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams, and by the Department of Energy under Grant DE-SC0021092.
The bright­ness of elec­tron beams emit­ted from pho­to­cath­odes plays a key role in the per­for­mance of x-ray free elec­tron lasers (XFELs) and ul­tra­fast elec­tron dif­frac­tion (UED) ex­per­i­ments. In order to achieve the max­i­mum beam bright­ness, the elec­trons need to be emit­ted from pho­to­cath­odes with the small­est pos­si­ble mean trans­verse en­ergy (MTE). Re­cent stud­ies have looked at the ef­fect that a graphene coat­ing has on the quan­tum ef­fi­ciency (QE) of the cath­ode [1]. How­ever, there have not yet been any in­ves­ti­ga­tions into the ef­fect that a graphene coat­ing has on the MTE. Here we re­port on MTE and QE mea­sure­ments of a graphene coated Cu(110) sin­gle crys­tal cath­ode at room and cryo­genic tem­per­a­tures. At room tem­per­a­ture, a min­i­mum MTE of 25 meV was mea­sured at 295 nm. This MTE re­mained sta­ble at 25 meV over sev­eral days. At 77 K, the min­i­mum MTE of 9 meV was mea­sured at 290 nm. We per­form den­sity func­tional the­ory (DFT) cal­cu­la­tions to look at the ef­fects of a graphene coat­ing on a Cu(111) sur­face state. These cal­cu­la­tions show that the graphene coat­ing re­duces the ra­dius of the sur­face state, al­low­ing for emis­sion from a lower trans­verse en­ergy state in com­par­i­son to bare Cu(111).
[1] F. Liu et al, Appl. Phys. Lett. 110, 041607 (2017); https://doi.org/10.1063/1.4974738
 
DOI • reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA66  
About • Received ※ 28 July 2022 — Revised ※ 19 July 2022 — Accepted ※ 07 August 2022 — Issue date ※ 10 August 2022
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