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Bright sources of radiation and high energy electrons
using gas, solid and nano-structured targets irradiated by
short intense laser pulses
M. Agranat, N. Andreev, S. Ashitkov, A. Emelianov, A. Eremin, V.
Fortov, A. Frolov, E. Gurentsov, O. Kostenko, S. Kuznetsov,
A.Ovchinnikov, O. Rosmej 1, A. Shevelko, D. Sitnikov
Joint Institute for High Temperatures
Russian Academy of Sciences, Moscow
JIHT RAS
1GSI-
Darmstadt research center with ion and laser beams
Workshop on High Energy Density Physics with Ion and Laser Beams
Organized by EMMI, GSI and JIHT RAS
November 21 - 22, 2008
Outline
 Introduction
 PHELIX status and where we are
 Laser wakefield electron acceleration by PHELIX
 in guiding structures
 In gas jets
 Ion sources by optical field ionization
 residual ion energy
 ponderomotive acceleration
 X-ray radiation using solid and nano-structured
targets
 mechanisms of hot electrons production
 optimization of Kα x-ray yield
 Powerful sources of terahertz radiation
 terahertz radiation in magnetized plasma
 low-frequency transition radiation
 Mega-gauss magnetic fields in laser plasmas
 Long high-energy pulses of 1- 20 ns duration at 400 - 1000 J energy
Beam-time 08.12 – 19.12.08
 Short high-power pulses of 1 – 10 ps duration at 100 J energy
 Short high-power pulses of 0.4 – 10 ps duration at 500 – 50 TW power
where we are with PHELIX intensity
focus intensity (W.cm-2), 100 J, 1 ps pulse
19
x 10
-150
-100
2
75% in 50 mm*
1.5
Y,mm
-50
EL= TV/cm
0
1
50
100
150
200
0.5
Strehl ratio: 0.3
-150 -100 -50
0 50 100 150 200
X,mm
0
Interaction of short intense laser pulses with ionizing gases
JIHT RAS
Residual Electron Energy
3
10
electron energy [eV]
laser pulse parameters:
IL=1016 W/cm2, tL = 13 fs
atomic potential:
U(y)= -1.61 exp(-y2), U1=24.6 eV
Qe(t),
quantum
2
10
1
10
Qfin(t)
"semi-classical"
single particle calculation
0
10
-1
10
-10
-5
0
(x-ct)/l0
5
“semi-classical” single particle model
t
P (t )  N (t )   P(t , t * , p * )(t * , p * )d 3 p * dt * ,
1

t
Q(t )  N (t )   Q(t , t * , p * )(t * , p * )d 3 p * dt * ,
1

k (p  , t )d 3p 
1 Ea.u.
~
 E
(t )

Jk
p 2  Ea.u.
~
Wk ( E(t ) )  exp 
~
JH
 2mJ H E(t )

Jk 
d 2 p*
 ( p*E~ )dp*E~
JH 
2mJ H

10
Expected potential
JIHT RAS
of laser – plasma acceleration of electrons
Electric field of plasma wave (with phase velocity ~ c, lp=2c/wp):
EP [V/m] ≈ 102  ( ne [cm3] )1/2   g1  w p / w0
= n / n0 – plasma wave amplitude; at  = 0.31.0, ne=10171018 cm-3:
EP = 10 100 GV/m
maximum of accelerating gradient
in traditional accelerators (RF linac):
ERF ~ 10 - 100 MV/m
Exponential growth of “the Livingston
curve” began tapering off around 1980
Laser-Plasma Acceleration of electrons
with record gradients ~ 10 GV/m
JIHT RAS
Z Axis
ensity
Normalized laser pulse int
and wakefield potential
0.50
laser pulse
injected electrons
wakefield potential
0.25
0.00
-0.25
0
2
=
xis
XA
4
6
k pr
8
10
5
0
10
15
25
20
)
- Vgt
Y Axis = k p(z
The result of optimization of laser and plasma parameters
for the monoenergetic acceleration of a short electron bunch in the wakefield
generated by the 50 TW, 100 fs laser pulse in the plasma channel
Parameters and results of some experiments
ctL≈lp/2
for standard LWFA scheme
P (TW)
I (W/cm2)
tL (ps)
l (mm)
Ne (cm-3)
DE (MeV)
Eac (GV/m)
Japan (KEK)
8
1017
1.0
1.05
1015
5
0.7
France (LULI)
12
4×1017
0.4
1.05
2×1016
1.5
1.5
Japan (JAERI)
2
8.4×1017
0.05
0.8
1018
France (LOA)
30
3×1018
0.03
0.8
2.5×1019
for Self-Modulated LWFA scheme
P (TW)
I (W/cm2)
20
200
200
ctL>>lp
tL (ps)
l (mm)
Ne (cm-3)
DE (MeV)
Eac (GV/m)
UK (RAL)
25
1019
0.8
1.05
1019
100
France (CEA)
5
1019
0.3
1.05
1020
20
USA (CUOS)
4.5
1018
0.4
1.05
1019
30
100
USA (NRL)
2.5
4×1018
0.4
1.05
3×1019
100
100
3
1017
1.0
1.05
1019
17
30
Japan (KEK)
100
Nonlinear Resonant Excitation of
the Wakefield in Plasma Channel
JIHT RAS
z = 6.7 cm
1.0
0.8
2.0
0
0.6
1.5
0.4
0.2
1.0
0.0
0
0.5
1
=
2
r
k p0
3
4 0
10
40
30
20
t)
(z - c
k
0
= p
50
50
=
k
40
p0
30
(z
-
3
20
ct)
2
10
0
1
0
k p0r
=

CO2 laser: l = 10.6 mm, PL= 2.5 TW, t = 2 ps, rL= 101 mm, PL/Pcr=0.16
N0=1.1×1016cm-3, Rch= 202 mm, Lch= 7 cm
PHYSICAL REVIEW SPECIAL TOPICS - ACCELERATORS AND BEAMS, VOLUME 6, 041301 (2003)
4 0.0
n(, ) / N
|a(, )|
2.5
JIHT RAS
Physical Restrictions on the Energy of
Accelerated Electrons in Laser-Plasma Accelerators
Maximum length of acceleration:
la  Ldeph 
Energy gain:
Laser Pulse Diffraction:
2(c v ph )
c   g2 l p ,
g 
w0
n
 c
wp
ne
eD
DWe  eEala 
la  2mc2 g2
lp / 2
Ldiff   Z R 
for LWFA
lp
2 2 rL2
l
, a02  PL / rL2
  a02
 l [mm]
DWdiff [ MeV]  960
P [TW]
t [ fs]
JIHT RAS
Main Processes Accompanying the Propagation
of Short Intense Laser Pulses in Gases
Typical parameters
Laser pulse:
Imax>1015W/cm2
,
FWHM < 1 ps,
l ≈ 1 mkm
Gas:
comparatively light atoms Z < 10, nat<1019cm-3
Laser Pulse
Electron Density
•REE
•DIL
Plasma
Laser Pulse
Distortions:
•LASRS
•RS-F & S-M
•Filamentation
•Diffraction
•Refraction
Gas
Ultrashort pulse
of high-frequency
Wake field
harmonics
 = z - ct
Kinetic equation for electron distribution function
f (r,p, t )
 f  (v) f  e(E  1[vH])  f  (r,t ) (p)  St 
 
t
c
p
  w 2mU / e E < 1  tunnel ionization (p)
Keldysh parameter
w is the laser radiation frequency, U is the ionization potential of atom or ion,
m (e) are the electron mass (charge), E is the electric field of the laser pulse.
ionization rate:
Z 1
  W N
k 1 k
k 0
and Ion Kinetics:
 N0
 Nk
 NZ
 W1N 0 ,
 Wk 1N k  Wk N k 1 ,
 WZ N Z 1
 t
 t
 t
Wk+1 is the (ADK) probability of tunnel ionization per second of the ion with
the ionization degree k (k = 0 corresponds to a neutral atom), No is the density of ions.
Cold Electron Hydrodynamics
Integration of the kinetic equation over p gives an equation for electron charge density:
e (r,t )  e d 3p f (r,p,t ) 
Where
J(r, t )   d 3p v f (r,p, t )
 e
 div J  e
 t
is the electron current density:
e
J2
J 1
J
e
J2 
1
1

 ( J ) J  J div =
1
J( JE) 
J
 E + [JH ] 
e m
 t e
e2c2  e c
ec2
  3
c2



e

NEW
The influence of ionization to the momentum density takes place
in the lower order of nonlinearity:
 Pe

1
 ( Ve )Pe  Pe  e (E  [VeH])
t
ne
c
Maxwell equations in the presence of ionization processes
rotH 
4
1 E
(J + J
)

ion
c
c t
IONIZATION
Ionization current (nonlinear polarization during ionization)
E Z 1
J ion  2  W k 1N kU k
E k 0
fulfills the energy and momentum conservation laws:
Z 1
 wk ,w  N k ,w

w    Wm 1 N mU m
t
t
m 0
and charge conservation relations for
the ionization charge density ion:
 ion
t
 div Jion  0
Z 1
 S  N k ,w
k


k


W
N
U

m

1
m
m
 t c2
t
w
m 0
as well as for full free charge density
Z
(r, t )  e d 3p f (r, p, t )  e  mN m

 div J  0
t
m 1
Electron Acceleration in the
Focus
Laser Parameters:
l01.053 tFWHM=300 fsec
w0=100 mm
IL=2x1018W/cm2, EL=190 j
Plasma Density:
ne=2.5 1016cm-3
g=200
Injected Electrons with Einj=g mc2 are accelerated to E~0.8
Length of acceleration la~Ldiff~10 cm
GeV,
How to Increase the Final Energy of Electrons or Emitted Radiation?
- By Optical Guiding to Overcome Diffraction!

By Self- focusing (?):

P  Pcr  1.7 10 2  g2 [ TW ]
g2 < 59  P[TW]

In Plasma channels or/and optical waveguides(!):
DWch [ Mev]  30( lp / rL )2 P[TW]  1.2 103 P[TW] / (kp rL )2
The possibility to produce plasma channels (or guiding):
- Plasma Channels in “free space”: gas filled chambers
o by axicon focusing or ionization channeling
- Capillary Waveguides:
o “Burned” capillary (Capillary discharge; Fast Z-pinch discharge);
o “Cold” capillary waveguides (gas filled tubes, OF Ionization).
• eigen (main) mode propagation (rL~Rcap – limited contrast)
• wide capillary with gas density depletion: high contrast
JIHT RAS
Laser pulse channeling in a capillary waveguide
Nm
u
u
~
E (r )   Cn J 0 (kn r ), kn  n  i s 2
n 1
a
k w a
Laser pulse
a
2
Cn 
E (r ) J 0 (un r / a) rdr , J 0 (un )  0
2 
a J1 (un ) 0
for the Gaussian laser pulse
E(r) =E0exp(-r2/r02)
Energy coupling to the main mode
98% at r0/a=0.645
Laser energy leakage:
IL(z) = I0exp(- z / LD)
w>1
z
1
D, n
L
2a
un2 1   w
 2 3
k0 a  w  1
Laser Wakefield Electron Acceleration
JIHT RAS
Focusing system
Accelerated electrons
Plasma
Qb  100pC
Ne-bunch  109
Electron
injector
Wake wave
Laser pulse
l0 = 1.053mm
tFWHM = 300 fs
w0=200 mm
EL=150 j
ne=1.71016 cm-3
E ~ 2.7 GeV/м
B. Cros, et al. Schematic view of the experiment
at the Lund Laser Center
Ltrap~10 cm, Lacc~ 1 m
Wakefield generation by guided laser pulses
spectroscopic diagnostics of the wakefield
JIHT RAS
Frequency Shift of the Pump Pulse
0.0
1.0
pump:
z=0
z = 1 cm
z = 3 cm
z = 6 cm
0.8
pump: red frequency shift
w>1
-0.5
-1.0
Dw/ wp
0.4
-1.5
analytical
modeling
-2.0
0.2
z
-2.5
0.0
2a
-3.0
760 780 800 820 840 860 880 900 920 940 960 980 1000
0
10
20
l [nm]
30
40
50
60
z [mm]
Spectrum Modulation of the Probe Pulse
Short intense laser pulse
at the capillary entrance, z = 0.
full scale modelling
analyt approximation, Eq. (17)
1.0
z = 4 cm
0.3
Wakefield
Diagnostic
laser pulse
0.2
I(w)
0.8
Y (r =0, )
I(l)
0.6
Laser pulse
0.6
0.4
0.1
0.2
0.0
0.0
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1
0
1
2
3
4
5
6
7
8
9 10
Dw / wp = (w-w0) / wp
-0.1
-40
-20
0
wp = wp(t - z/c)
20
40
A ( z)  Cr
k0
k p2 z
  1 2 
sin 
2
  4 1 



1
I ( z )  I ( z  0)
Long low-energy electron bunch will be trapped and compressed
in the wakefield
1.0
p=100, kpr0=3.35, kpl0=2.355
0.8
0.6
0.8
laser pulse
boundary of
focusing phase
0.6
0.4
a(r=0, )
|e|/mc
2
1.0
0.4
2
Einj / mc =5.43
0.2
0.2
electron bunch
0.0
0.0
-0.2
-0.2
0
5
10
15
20
25
=kp(z-Vt)
N.E Andreev., S.V. Kuznezov. Electron Bunch Compression in Laser Wakefield Acceleration.//
http://icfa.lbl.gov/icfapanel.html/Newsletter/Special Issue: Giens Workshop Proceedings, June 24 - 29, 2001.
Computer simulation by the code
LAPLAC
JIHT RAS
Results of full scale modeling including
laser pulse dynamics, gas ionization and bunch loading
0
10000
20000
30000
40000
0.10
4000
40
35
3000
0.06
2000
0.04
1000
n [mm*mrad]
2
30
< > / mc
2 Drms / < >
0.08
25
20
15
10
0.02
5
0.00
0
0
10000
20000
30000
40000
0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Lacc / Lph
kpzacc
Parameters of the laser pulse and electron bunch
a0 
e EL
mcw
1
 ph  w / w p  100 Einj  10 MeV Lb  1.26 k p1
Rb  0.15 k p1
0.7
PWFA and LWFA Afterburning for High Energy Physics and Hard X-rays
C. Joshi and T. Katsouleas, Physics Today, 2003
a pair of PWFA energy doublers, installed on either side of the collision point of the Stanford
Linear Collider (SLC), that serve to double the energies of the electron and positron beams
from the present 50 GeV to 100 GeV.
after-burning ERLP-electrons using Laser Wakefield Acceleration (LWFA)
amplified electron bunch
electron bunch
x-ray`s
electron injector
beryllium window
35 MeV
ASTeC
Capillary / gas jet
>350 MeV
[email protected]
Interaction of short intense laser pulses with ionizing gases
JIHT RAS
Multi-group Residual Electron Energy Distribution
of many-electron atoms
-2.0
-1.5
-1.0
-0.5
0.0
4
10
0.5
7
6
3
3
laser pulse parameters:
IL=1019 W/cm2, tL = 70 fs,
l=0.78mm
2
Nitrogen gas
5
2
10
4
1
10
Zeff
Te [eV]
10
0
10
1
-1
10
-2.0
-1.5
-1.0
-0.5
0.0
0
0.5
t / 70 fs
Energy of electron groups and relaxation times (N2=1.5×1019 W/cm2)
k
1
2
3
4
5
Qe,k [eV]
3.3
9.7
23.4
79.5
120.
tee,k
60 fs
150 fs
380 fs
1.8 ps
2.6 ps
6
7
39103 39103
13 ns
13 ns
Ion sources by optical field ionization
JIHT RAS
produced by
A large amount of ions with low temperature (less than 100 eV),
low momentum spread and narrowed charge state distribution
can be produced by petawatt-class short-pulse laser
JIHT RAS
X-ray radiation of laser plasma
Focusing system
1240 nm, 80fs,
10 12 W, 10 Hz
~10 18 W/cm2
X-ray Hamos
Spectrometer
X-ray
Vacuum camera
Mg, Cu target
Measurement of
the reflected pulse
X-ray radiation using solid and nano-structured targets
JIHT RAS
Optimization of Kα x-ray yield
K radiation from Cu laser-produced plasmas
Cr:Forsterite laser system, w0, p-polarization,
EL=30 mJ, tL = 80 fs, 1016 ÷ 1017 W/cm2
INTENSITY, 10 10 phot/A sr
15
8
4
20
N (10 phot)
Single laser short experiment
model
experiment
25
K1
Cu
sho t #2 3m-16
K
2
10
5
0
0
5
10
15
20
25
30
35
40
Ep, mJ
0
1.50
1.5 2
1.54
1.56
WAVE L ENGT H, A

E0  EL 1  (1  f 
1/ 2
sin 
Th, keV  7.6I L,16l2mm 2 sin 2 
The model calculation of Kα yield against pulse
energy in comparison with experimental data
received at IHED laser facility:
λ = 1.24 mm, tp = 80 fs,
df = 10 mm,  = 45, Fe target
E0 – driving, EL – laser field, f –absorption,  =
1.57, IL,16 = IL/1016 W/cm2 – laser intensity
There is a range of laser pulse parameters in which Kα yield may be described by
vacuum heating mechanism
nano-structured targets
Fe clusters on Cu target
JIHT RAS
A.V. Eremin Laboratory
X-ray radiation using solid and nano-structured targets
produced by
JIHT RAS
Fe clusters on Cu target
E0  3EL cos 1
40
40
flat target
clustered surface
N (10 phot)
30
20
20
8
8
N (10 phot)
30
flat target
clustered surface
10
10
0
0
15
20
25
30
35
40
45
50
 (deg)
Dependence of Kα yield on angle of
incidence for peak intensity 31017 W/cm2
5
10
15
20
16
I0, 10 W/cm
25
30
2
Dependence of Kα yield on peak intensity
for angle of incidence 30
Th,keV  68.41 I L,16lm2m cos2 1
Enhancement of driving electric field at a cluster surface and favorable
conditions for Kα photons to escape from the wafer lead to considerable
enhancement of Kα yield
Powerful sources of terahertz radiation
produced by
JIHT RAS
SiO2 aerogel, ρ=0.02 g/cm-3
Magnetic field (ωp>>Ωe=eB0/mec)
Vacuum Chamber
ω
0
z
0
THz
ω
Lens
Mirror
N0e >Ncr=meω02/4πe2
Capillary
tube
Solenoid
Laser
Window
0
0
z
THz
 THZ  1 t  1THz
THz
radiation
WTHz
w02 VE2 WL
 2 2 2 2
w p c w pt
 THZ  w p 2  1THz
dWTHz
0.5
 2 2
dz
w0 t

1  2
 k 2R2
p L

 VE2 WL

 4c 2 L

Laser: λ0=1.053mm; τFWHM=0.5ps; IL=2·1018 W/cm2; RL=50 mm (WL=100J)
Plasma: N0e=6·1021 cm-3; ωpτ=1200
Plasma: N0e=1.4·1016 cm-3; ωp =6.7 ·1012 s-1
THz: PTHz ≈ 30 MW; WTHz ≈ 10mJ;
WTHz/WL≈ 10-7
THz: WTHz/WL≈3·10-4z[см];
z=10см :
PTHz≈10GW; WTHz≈0.3J; WTHz/WL≈3·10-3
Mega-gauss magnetic fields in plasmas
JIHT RAS
B
produced by
Circularly polarized
Laser pulse
w p VE2 / c 2
eBz

me cw0 2w02 (1  VE2 / c 2 
2
For relativistic laser intensities, VE
at critical density, w p  w0
/ c 1
e  w0
Laser: λ0=1.053mm; τFWHM=0.5ps (τ=0.3ps); IL=3·1019W/cm2 ; RL=15 mm
(WL=100 J; PL= 300 TW)
gas: N0e=3·1019cm-3 → Bz≈ 3МГс ;
aerogel: N0e~1021cm-3 → Bz≈ 100 MGauss
  1.8 107 B0[G]s 1 w p  6.7 1012 s 1   0.1w p  B0  3.7 104 G
Thank
You for attention!
JIHT RAS
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Filamentation instability of short intense laser pulses
 analytical theory and predictions
JIHT RAS
The solution leads to the following expression by inverse Laplace transform of intensity perturbation
 i  0
(
1
dp p ig (q 
I ( , , q   I 0
e e
 e ig (q 

2 i i0 p

g (q  
q2
l2
1
2
1 p2
If diffraction exceeds the non-linear effects, l<p, we obtain from above equation for q<1
1/ 3
I ( , , q 
2

2 2
I 0
6 a0 
(

1/ 6
1/ 3 
1/ 3

2 2
 2
2 2

3 3  a0     q  3  a0  
11 

exp
cos


 4  4    2
4  4 
12 

 

in the opposite limit of longer wavelength perturbations, where the nonlinear effects exceed diffraction
I (q 
1  


q(qb3  q 3  

I 0
2  2

1/ 2


exp 
q qb3  q 3  ,
 2

(

qb  2 (a0  /  
1/ 3
(
The growth rate of dynamical filamentation has a maximum for qmax  k max / k p  a0 |  | /( 2 )
The corresponding maximum growth rate
Gmax  3 2
5 / 6
(

2 2 1/ 3
a0  
N.E. Andreev, L.M. Gorbunov, P. Mora, R.R. Ramazashvili,
Phys. Plasmas 14, 083104 (2007)

1/ 3
Filamentation instability of short intense laser pulses
 numerical modelling results and estimations
JIHT RAS
Contour plots of intensity perturbations and of spectrum of perturbations
for different pulse propagation distances z = 100, 300, 600
Contour plots of normalized electron
density perturbations at z = 600
R
for a laser pulse with radius R
our consideration is limited by
the propagation distance
 < (k p R /  )3 a0b / 2
for exp growth N>>1
  2(2 / 3) 3 / 2 N 3 (a 0 b ) 2
a0b (k p R)  2 N / 3
N.E. Andreev, L.M. Gorbunov, P. Mora, R.R. Ramazashvili, Phys. Plasmas 14, 083104 (2007)
Wakefield generation by guided laser pulses
Nonlinear Plasma Response
JIHT RAS
To describe the slowly varying motions and fields in plasma we use Maxwell's equations
and the relativistic hydrodynamic equations for cold plasma electrons
with allowance made for the process of tunneling gas ionization:

p
1 mc 
1
2

 
 eE  mc 2   0 p 
 0 a  Re2 (a  a  e z
t
n
2 n 
2

 n0
n
1 B
E
 div (nv)  0 
 4env  c rotB rotE  
t
t
c t
t
In the quasi-static approximation by using the dimensionless commoving variables:
S 

1 2  1
(e z   q)  E     0  q  a e z   Re S 2 a   a  e z

 
2
 8

  2E
 
(u z  1)     ( u )  S 0    0
     E 
( u )

2








 (
S0 
0
N0w p 0

na
N 0w p 0
Z n 1
 Wk Dk 
k 0
Z n 1
S
k 0
(k )
0
S2 
,
2
N 0w p 0

 2m S 0
The normalized ionization current can be explicitly expressed through the harmonics of the ionization source:
G
( ion)
4e (ion) k p 0  2a


J

k0  a 2
mw 2p 0 c

Z n 1
S
k 0
(k )
0
Uk
a 
 S2 
mc 2 4 

JIHT RAS
Nonlinear plasma response – Effective Potential
The nonlinear relativistic plasma response can be expressed through a single scalar function (potential)  :
  0  D

    S
2
a
 0 
m
 S   
 1
 Re a *  a *
 0    
4
4
1

2
a
S 0 
m
    qz  
qz 
 Re a *  a *
 
2
4



(
(

d 




d     q   
z
S



The electric and magnetic fields in plasma can be also expressed through the potential :
Ez 

,

E r  B 

,

For a wide (in comparison with the plasma skin depth 1/kp) laser pulse
the equation for the potential can be linearized with respect to the small parameter |   1 | /( k p L ) 2


 02
 2  ln  0  3
  0 D   
(D    0 ) 2 
2

  
2


2

 
1 a
2
0

D
a
1 


2
4
(







S
TIME EVOLUTION OF LASER INTENSITY
EL.ENERGY,ev
Quantum gravitation,
quantum electrodynamics
ELI
a~
1027
g
-B.HOLE
Е ~ 0.1PW/m
FELIX
JIHT
Н~340MGs P~300 Gbar
Ponder P~Hydro
P~1Mbar
Sun-5.6 103 W/cm2
K radiation from laser-produced plasmas
Cr:Forst laser system
1.24 μm, EL=100 mJ, 80 fs, 1016 ÷ 1017 W/cm2
Cu
12
K1
8
K
4
0
1.5 32
Fe
K1
6
K
11
shot # 23n - 11
Intensity [10 phot / A ster]
Intensity [10 10 phot / A ster]
8
s hot # 23n-28
4
2
0
1.5 36
1.5 40
1.54 4
1.54 8
1 .93 0
1.935
Wavelengt h [A]
1.940
Wav len g th [A]
Single short X-ray spectrum
1.945
1.950