Tunable Plasma-Wave Laser Amplifier

Transcription

1 Tunabl Plasma-Wav Lasr Amplifir A. DAVIES, S. BUCHT, J. BROMAGE, J. D. ZUEGEL, and D. H. FROULA Univrsity of Rochstr, Laboratory for Lasr Enrgtics R. TRINES R. BINGHAM P. A. NORREYS AND J. SADLER Ruthrford Applton Laboratory Univrsity of Strathclyd Univrsity of Oxford EPW Limitation Yar Author Ipump Pump Epump Dtpump 14 lasr (ps) (10 W/cm2) Facility mp Pu d S d fi i l p Am b pro av w a sm Pla narrowband gratings d t l mp pu D ~2.5-J/cm2 damag thrshold Powrful lasrs: fmtosconds p Tim multilayr dilctric coatd broadband gratings gold gratings Raman amplification Rsonanc condition: ~pump = ~sd + ~plasma M. Drhr W. Chng Max Plank Ti:Sa Princton 140 Ti:Sa J. Rn Princton Ti:Sa (7.8) 2007 J. Rn Princton Ti:Sa (5.9) 2012 D. Turnbull Princton Ti:Sa X. Yang Univrsity of Strathclyd 2015 Particl longitudinal vlocity vrsus spac Finit tmpratur affct on wav braking V (x) Vph t2 t1 Ti:Sa t3 0.8 x Prvntion 0.4 E25522 Summary Pump Limitation Th capabilitis affordd by th lasrs and diagnostics at LLE will allow for multipl aras of nw xploration into th fild of Raman amplification Stimulatd Raman backscattr from thrmal nois can dplt th pump nrgy bfor raching th sd puls Sd ionization о о Pump dpltion о о о 0.4 Sd ionization Avoids pump limitations 2. Producs a vry cold plasma (<10 V) Elctron tmpratur (V) Th sd-ionization and pump-dpltion rgims will b ralizd at LLE for th first tim bcaus of our high-powr sd pulss. D. S. Clark and N. J. Fisch, Phys. Plasmas 10, 3363 (2003); T. P. Coffy, Phys. Fluids 14, 1402 (1971). E25524a Landau Rsonanc Wav damping (LD) dtuning braking Thrmal SRS Filamntation High nrgy 0.5 n 4/3 n c ^a pumph M. Drhr t al., Phys. Rv. Ltt. 93, (2004). W. Chng t al., Phys. Rv. Ltt. 94, (2005). J. Rn t al., Nat. Phys. 3, 732 (2007). D. Turnbull t al., Phys. Plasmas 19, (2012). X. Yang t al., Sci. Rp. 5, (2015). thrshold Rgim 1/2 E warm 1 8 1/4 1 2 / = 1 B B + 2B l 3 3 E cold b v osc 1 v ph ~0.15-J/cm2 damag G11058 Efficincy n DTsd (ovrlap) /~ ~ (1018 cm 3) pump p (fs) (%) Esd (nj) Thr ar thr paramtr rgims of intrst whr potntially nw xprimntal progrss can b achivd in th fild of Raman amplification Sd powr Tchnological novlty Enrgtic lasrs: picosconds At high amplituds, th EPW can brak if th particl vlocity carrying th wav approachs th wav s phas vlocity Th bst xprimnts to dat hav only rachd nrgy-transfr fficincis of <10% Ewarm WB/Ecold WB Plans for a tunabl Raman amplifir at th Laboratory for Lasr Enrgtics E25525a A larg paramtr scan ovr pump intnsitis and dnsitis has bn run in particl-in-cll (PIC) to study th ffct of wav braking Th high-nrgy rgim aims to produc th highst nrgy amplifir using th maximum nrgy of th pump: 50 J c SRS = a pump ^~ pump ~ ph1/2 M. Drhr W. Chng J. Rn Dv SRS = c SRS /2r Effct of chirp G = xp ^Dv SRS t limh t lim = Dt pump E25519a G T = 0 V D. Turnbull X. Yang T = 400 V 1.0 ng 0.8 i ak av W J. Rn T = 100 V br LLE 0.4 Ionization Ionization 0.2 g kin a br v Wa n/nc n/nc Dv SRS Dv pump Advantags Most-nrgtic amplifir DmSRS Dmpump G Possibility of producing a mdiumrang Raman amplifir (first) Disadvantags n/nc Fighting all prviously mntiond limitations E25529a Ionization 0.01 High nrgy q Landau ~ p = d m n 0 Exprimnts ar hindrd by many plasma-physics phnomna that ar difficult to prdict and thrfor rquir carful masurmnt Th charactristics of th pump and sd lasrs at LLE mak it possibl to accss rgims that wr not possibl in past xprimnts, whr much of th limitations of Raman amplification ar avoidd 1/2 Dmpump SRS 2 n DmSRS Ipump Isd n Epump Diamtr Dtpump Esd Dtsd (ps) (fs) (1014 W/cm2) (1014 W/cm2) (1018 cm 3) Dtun Gnral SRS apump Th promis of Raman amplification to amplify and comprss short pulss to high pak powrs in a plasma has largly bn containd within thory and simulations Rgim 1-D, constant pump, constant dnsity, sd mts nonlinar rgim I # m 2nm 1/2 n a0 = d 1.3 # kmd (50 V) kmd (150 V) E25534a E25531a Tmpratur is an xtrmly important paramtr to Raman amplification and has bn th last diagnosd in xprimnts so far Th sd-ionization rgim taks advantag of our intns sd to produc th plasma, thrby avoiding th pump limitations EPW Limitation Th primary application of Raman amplification is to produc PW-scal lasr pulss not limitd by th damag thrsholds of grating comprssors Th pump chirp dtuns th rsonant intraction, which can rduc th fficincy of nrgy transfr in th pump-dpltion rgim Incrasing tmpratur Physics milstons LLE objctivs Amplification of sd Strong coupling btwn pump and sd mdiatd by an lctron plasma wav (EPW) Rach pump dpltion Dmonstrat that th slic fficincy of a Raman amplifir can b high (>30%) Efficint amplifir Dvlop advancd diagnostics to idntify limiting phnomna Pump chirp M. Drhr Dvlop mitigation stratgis Idntify an mpirical optimal paramtr rgim for fficint Raman amplification Elucidat th road map to scaling to larg lasr systms basd on ths rsults High-fidlity sd Dmonstrat that th amplifid sd has good wavfront and tmporal charactristics rquird for xprimnts (focusability, contrast, tc ) incrass th ffct of Landau damping grossly changs th optimal rgim avoiding wav braking Changing tmpratur as th pump hats th plasma can dtun a rsonanc in th linar rgim J. Rn 0.38 In litratur D. Turnbull 0.25 X. Yang 0.43 LLE J. Rn Effmax < 1 q strongly rducs th thrshold for thrmal and pondromotiv filamntation 0.09 W. Chng 613 Dm cm 3 1/ W/cm 2 q. m c n Dt ^psh m Im 2 ^nmh Dmonstrat pump dpltion across th ntir amplifir such that th ovrall fficincy is high (>30%) E25520a rducs gain for SRS (good for thrmal SRS, bad for sd in linar rgim) q Isd (1014 W/cm2) Epump Sd ionization Ipump Dtpump Diamtr (1014 W/cm2) (ps) Epump n 18 (10 cm 3) Advantags Avoid pump limitations no mntion of tmpratur analytic stimat basd on invrs brmsstrahlung hating (many diffrnt modls) At LLE w plan to build a tim rsolvd Thompson scattring diagnostic (~2 ps rsolution)* E25526a Tst of sd ionization (first) Possibility of producing a mdium rang-raman amplifir (first) Disadvantags Fighting all prviously mntiond limitations Absolut tmpratur masurmnts vrsus tim ar xtrmly important for th intrprtation of rsults. N. Yampolsky and N. Fisch, Phys. Plasmas 18, (2011). E25523a Rgim *A. Davis t al., UO , this confrnc. E25532a EPW Limitation Thr ar many phnomna that can intrrupt th Raman amplification procss Pump: Amplification EPW: Pump dpltion Thrmal forward raman scattring SRS growing from thrmal nois can dplt th pump and dgrad amplifid sd contrast Nonlinar ffct whr lctrons dphas from th EPW, dstroying th cohrnc of th structur Intns sd can dcay into a forward-propagating photon and backward-propagating EPW Filamntation Rsonanc dtuning Thrmal or pondromotiv filamntation dgrads th pump puls wavfront Rsonanc condition not satisfid ovr th whol intraction (pump chirp, dnsity gradints, tmpratur gradints ) Wavfront dgradation causd by filamntation drivn by a rlativistic mass incras of lctron Landau damping Collisionlss damping of th EPW k EPW m D # 0.29 ~/k f(v) Rlativistic filamntation/focusing M. Drhr m D \ T /n W. Chng J. Rn kmd (50 V) kmd (150 V) Sdin Pumpout Targt/gomtry Intraction drawn to scal f/26 focus, f = 120 cm 4 angl btwn bams Pumpin Gas cll 4 mm Hydrogn Sdout Wak sd (nois): LD damps th wav amplitud to zro Strong sd: LD rducs growth rat, incrasing th tim in th linar rgim D. Turnbull X. Yang long homognous plasma dnsity to cm 3 E25530a J. L. Klin t al., Phys. Plasmas 13, (2006). Pump Dpltion Isd Ipump Dtsd Esd Diamtr Dtpump Epump n (fs) (1014 W/cm2) (1018 cm 3) (1014 W/cm2) (ps) isolat scattring sourcs a sd Dt sd ~ sd ~ p ~5 Advantags Highst possibl fficincy, no linar gain (first) E23504d 0.9 ~pump /~p = 8 to 13 mcn Dm Emax Dt Pump 1053 nm 8 nm 50 J 1 to 100 ps Sd 1140 to 1200 nm 60 to 120 nm 75 mj 75 to 100 s fs Pump dpltion: LD is too slow to damp th wav E25521a Rgim Noncolinar intraction 0.40 J. Rn Th pump-dpltion (PD) rgim aims to produc th highst-fficincy amplifir possibl by dplting th pump from th bginning Gas cll ~/k Wakfild gnration An intns sd xpls lctrons, changs dnsity, dstroys rsonanc, and loss nrgy Th LLE xprimntal stup is dsignd to b flxibl to allow changing of paramtrs to follow fdback from xprimntal rsults f(v) Sd: Amplification limits Wavbraking Thrmal stimulatd Raman scattring (SRS) Landau damping (LD) is a wav particl intraction that transfrs nrgy from a plasma wav to particls that ar travling nar th phas vlocity of th wav S. Bucht t al., GP , this confrnc. Tst of pump-dpltion thory (first) Disadvantags Rquirs a small spot siz, thrfor littl nrgy in th pump E25533a PD M. Drhr 0.31 W. Chng 0.28 J. Rn 0.32 J. Rn 2.0 D. Turnbull 0.27 X. Yang 0.60 LLE-PD 5.07

2 Plans for a tunabl Raman amplifir at th Laboratory for Lasr Enrgtics Tchnological novlty Enrgtic lasrs: picosconds p m Pu d S d lifi p Am b pro v a aw m s Pla Tim p D td l p m pu narrowband gratings multilayr dilctric coatd ~2.5-J/cm2 damag thrshold Powrful lasrs: fmtosconds broadband gratings gold gratings ~0.15-J/cm2 damag thrshold G11058 Raman amplification Rsonanc condition: ~pump = ~sd + ~plasma

3 Summary Th capabilitis affordd by th lasrs and diagnostics at LLE will allow for multipl aras of nw xploration into th fild of Raman amplification Th promis of Raman amplification to amplify and comprss short pulss to high pak powrs in a plasma has largly bn containd within thory and simulations Exprimnts ar hindrd by many plasma-physics phnomna that ar difficult to prdict and thrfor rquir carful masurmnt Th charactristics of th pump and sd lasrs at LLE mak it possibl to accss rgims that wr not possibl in past xprimnts, whr much of th limitations of Raman amplification ar avoidd E25519a

4 Th primary application of Raman amplification is to produc PW-scal lasr pulss not limitd by th damag thrsholds of grating comprssors Amplification of sd Strong coupling btwn pump and sd mdiatd by an lctron plasma wav (EPW) Rach pump dpltion Dmonstrat that th slic fficincy of a Raman amplifir can b high (>30%) Efficint amplifir Physics milstons Dmonstrat pump dpltion across th ntir amplifir such that th ovrall fficincy is high (>30%) LLE objctivs Dvlop advancd diagnostics to idntify limiting phnomna Dvlop mitigation stratgis Idntify an mpirical optimal paramtr rgim for fficint Raman amplification Elucidat th road map to scaling to larg lasr systms basd on ths rsults High-fidlity sd Dmonstrat that th amplifid sd has good wavfront and tmporal charactristics rquird for xprimnts (focusability, contrast, tc ) E25520a

5 Thr ar many phnomna that can intrrupt th Raman amplification procss Pump: Amplification EPW: Pump dpltion Sd: Amplification limits Thrmal stimulatd Raman scattring (SRS) SRS growing from thrmal nois can dplt th pump and dgrad amplifid sd contrast Filamntation Thrmal or pondromotiv filamntation dgrads th pump puls wavfront Wavbraking Nonlinar ffct whr lctrons dphas from th EPW, dstroying th cohrnc of th structur Rsonanc dtuning Rsonanc condition not satisfid ovr th whol intraction (pump chirp, dnsity gradints, tmpratur gradints ) Landau damping Collisionlss damping of th EPW Thrmal forward raman scattring Intns sd can dcay into a forward-propagating photon and backward-propagating EPW Rlativistic filamntation/focusing Wavfront dgradation causd by filamntation drivn by a rlativistic mass incras of lctron Wakfild gnration An intns sd xpls lctrons, changs dnsity, dstroys rsonanc, and loss nrgy E25521a

6 Th bst xprimnts to dat hav only rachd nrgy-transfr fficincis of <10% Yar Author Facility Pump lasr E pump Dt pump (ps) I pump (10 14 W/cm 2 ) E sd (nj) DT sd (fs) n (10 18 cm 3 ) ~ pump /~ p Efficincy (ovrlap) (%) M. Drhr W. Chng Max Plank Ti:Sa Princton Ti:Sa J. Rn Princton Ti:Sa (7.8) 2007 J. Rn Princton Ti:Sa (5.9) 2012 D. Turnbull Princton Ti:Sa X. Yang Univrsity of Strathclyd Ti:Sa E25522 M. Drhr t al., Phys. Rv. Ltt. 93, (2004). W. Chng t al., Phys. Rv. Ltt. 94, (2005). J. Rn t al., Nat. Phys. 3, 732 (2007). D. Turnbull t al., Phys. Plasmas 19, (2012). X. Yang t al., Sci. Rp. 5, (2015).

7 Pump Limitation Stimulatd Raman backscattr from thrmal nois can dplt th pump nrgy bfor raching th sd puls c ~ ~ a / SRS = pump^ pump ph 12 Gnral SRS Effct of chirp D v = c / 2r SRS SRS G= xp ^Dv t h t a 0 lim I # mn = d 13. # 10 = Dt pump 2 12 / m n / n ~ p = d m n 0 SRS Dv Dv lim SRS pump Dm SRS Dm pump M. Drhr W. Chng J. Rn J. Rn D. Turnbull X. Yang G E25529a

8 EPW Limitation Th pump chirp dtuns th rsonant intraction, which can rduc th fficincy of nrgy transfr in th pump-dpltion rgim q. Pump chirp 613 Dm 10 m t ps n c 10 c m D ^ h m m / Eff max < 1 q I 2 Wcm / ^nmh 14 2 q M. Drhr 0.09 W. Chng 0.4 J. Rn 0.26 J. Rn 0.38 D. Turnbull 0.25 X. Yang 0.43 LLE E25523a N. Yampolsky and N. Fisch, Phys. Plasmas 18, (2011).

9 EPW Limitation Landau damping (LD) is a wav particl intraction that transfrs nrgy from a plasma wav to particls that ar travling nar th phas vlocity of th wav f(v) k m 029. EPW D # km D (50 V) km D (150 V) f(v) ~/k m \ T / n D M. Drhr W. Chng ~/k Wak sd (nois): LD damps th wav amplitud to zro Strong sd: LD rducs growth rat, incrasing th tim in th linar rgim Pump dpltion: LD is too slow to damp th wav J. Rn J. Rn D. Turnbull X. Yang E25530a J. L. Klin t al., Phys. Plasmas 13, (2006).

10 EPW Limitation At high amplituds, th EPW can brak if th particl vlocity carrying th wav approachs th wav s phas vlocity V (x) Particl longitudinal vlocity vrsus spac V ph t 1 t 2 t3 n n c Prvntion v osc 1 v ph a / ^ h 4 3 pump x Finit tmpratur affct on wav braking E warm WB /E cold WB E E / warm 14 / 12 / 12 cold 1 8 = b1 B B + 2B Elctron tmpratur (V) l E25524a D. S. Clark and N. J. Fisch, Phys. Plasmas 10, 3363 (2003); T. P. Coffy, Phys. Fluids 14, 1402 (1971).

11 A larg paramtr scan ovr pump intnsitis and dnsitis has bn run in particl-in-cll (PIC) to study th ffct of wav braking 1-D, constant pump, constant dnsity, sd mts nonlinar rgim 0 T = 0 V T = 100 V apump 1.0 ng i ak av W br 0.6 LLE Ionization Ionization Ionization 0.2 ng aki br n/nc E25534a T = 400 V 0.01 v Wa 0.02 n/nc n/nc 0.0

12 Tmpratur is an xtrmly important paramtr to Raman amplification and has bn th last diagnosd in xprimnts so far Incrasing tmpratur rducs gain for SRS (good for thrmal SRS, bad for sd in linar rgim) strongly rducs th thrshold for thrmal and pondromotiv filamntation incrass th ffct of Landau damping grossly changs th optimal rgim avoiding wav braking Changing tmpratur as th pump hats th plasma can dtun a rsonanc in th linar rgim In litratur no mntion of tmpratur analytic stimat basd on invrs brmsstrahlung hating (many diffrnt modls) At LLE w plan to build a tim rsolvd Thompson scattring diagnostic (~2 ps rsolution)* Absolut tmpratur masurmnts vrsus tim ar xtrmly important for th intrprtation of rsults. E25526a *A. Davis t al., UO , this confrnc.

13 Th LLE xprimntal stup is dsignd to b flxibl to allow changing of paramtrs to follow fdback from xprimntal rsults Sd in Intraction drawn to scal f/26 focus, f = 120 cm 4 angl btwn bams Pump in Gas cll Targt/gomtry long homognous plasma dnsity Pump out Gas cll 4 mm Hydrogn Sd out to cm 3 ~ pump /~ p = 8 to 13 Noncolinar intraction isolat scattring sourcs m cn Dm E max Dt Pump 1053 nm 8 nm 50 J 1 to 100 ps Sd 1140 to 1200 nm 60 to 120 nm 75 mj 75 to 100 s fs E23504d S. Bucht t al., GP , this confrnc.

14 Thr ar thr paramtr rgims of intrst whr potntially nw xprimntal progrss can b achivd in th fild of Raman amplification Rgim Thrmal SRS Filamntation Landau damping (LD) Rsonanc dtuning Wav braking Sd powr High nrgy Sd ionization Pump dpltion о о о о о Sd ionization 1. Avoids pump limitations 2. Producs a vry cold plasma (<10 V) Th sd-ionization and pump-dpltion rgims will b ralizd at LLE for th first tim bcaus of our high-powr sd pulss. E25525a

15 Th high-nrgy rgim aims to produc th highst nrgy amplifir using th maximum nrgy of th pump: 50 J Rgim E pump Diamtr Dt pump (ps) I pump (10 14 W/cm 2 ) E sd Dt sd (fs) I sd (10 14 W/cm 2 ) n (10 18 cm 3 ) High nrgy Advantags Most-nrgtic amplifir Possibility of producing a mdiumrang Raman amplifir (first) SRS Dm SRS Dm pump G Disadvantags Fighting all prviously mntiond limitations Dtun q Landau km D (50 V) km D (150 V) E25531a

16 Th sd-ionization rgim taks advantag of our intns sd to produc th plasma, thrby avoiding th pump limitations Rgim I sd (10 14 W/cm 2 ) E pump Diamtr I pump (10 14 W/cm 2 ) Dt pump (ps) E pump n (10 18 cm 3 ) Sd ionization Advantags Avoid pump limitations Tst of sd ionization (first) Possibility of producing a mdium rang-raman amplifir (first) Disadvantags Fighting all prviously mntiond limitations E25532a

17 Th pump-dpltion (PD) rgim aims to produc th highst-fficincy amplifir possibl by dplting th pump from th bginning Rgim Dt sd (fs) E sd Diamtr I sd (10 14 W/cm 2 ) n (10 18 cm 3 ) I pump (10 14 W/cm 2 ) Dt pump (ps) E pump Pump Dpltion Advantags Highst possibl fficincy, no linar gain (first) Tst of pump-dpltion thory (first) Disadvantags Rquirs a small spot siz, thrfor littl nrgy in th pump E25533a a Dt ~ ~ ~ 5 sd sd sd p PD M. Drhr 0.31 W. Chng 0.28 J. Rn 0.32 J. Rn 2.0 D. Turnbull 0.27 X. Yang 0.60 LLE-PD 5.07