Setup and commissioning of a cryogenic system for the production of targets to be used in experiments with high energy lasers and heavy ion beams

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Setup and commissioning of a cryogenic system for the production of
targets to be used in experiments with high energy lasers and heavy ion beams
∗
J. Menzel
1
, A. Bla
ˇ
zevi
´
c
2
, D.H.H. Hoffmann
1
, A. Frank
1
, M. G
¨
unther
1
, T. Heßling
2
, M. Imran
1
,
A. Pelka
1
, M. Roth
1
, G. Schaumann
1
, D. Schumacher
1
, T. St
¨
ohlker
2
, and S. Udrea
1
1
TU Darmstadt;
2
GSI Darmstadt
The experimental investigation of the energy loss of
swift heavy ions in laser produced plasmas [1] is one of the
main research activities of the Plasma Physics Department
at GSI.
Cryogenic systems [2] are in this context of special in-
terest, due to the possibility to create solid state targets
(T = 4.2 K ) out of matter which is gaseous under normal
conditions, especially hydrogen and deuterium. Moreover,
the properties of laser produced hydrogen and deuterium
plasmas are well understood theoreticaly and thus highly
suitable for studying the physics of the interaction of ener-
getic heavy ions with plasma particles.
(a) U-shape (b) O-shape
Figure 1: Solid deuterium targets with 2 mm width
Cryogenic targets with different geometries have been
produced (Fig. 1). Targets with a high aspect ratio having a
thickness of only a few micrometers and transverse sizes of
millimeters are of special interest for the envisaged investi-
gations. Such targets allow the generation of laser plasmas
with a high degree of homogeneity, thus allowing measur-
ing the ion energy loss under well defined conditions in
fully ionized plasma.
Figure 2: Deuterium plasma produced out of an solid target
using the nhelix and Phelix laser systems
∗
Also supported by BMBF 06DA9034 I
Solid deuterium targets have been simultaneously irra-
diated by the high energy laser systems nhelix and Phelix
(50 J in 10 ns @ 1064 nm;1053 nm ) [3] (Fig. 2). The free
electron density inside the deuterium plasma has been mea-
sured for different times (Fig. 3).
(a) 9.1 ns after start of laserpulse (b) 11.9 ns after start of laserpulse
Figure 3: Free electron density of a deuterium plasma;
space in µm, electron density as colorbar in 10
19
cm
−3
To measure the thickness of deuterium targets an 14 keV
electron source with a subsequent focussing and steering
system has been set up. The evolution of the thickness be-
low 200 µm has been determined by analysing the electron
scattering. A precision of 12 % has been achieved within
the range of interest (50 − 15 µm) for energy loss experi-
ments (Fig. 4).
Figure 4: Evolution of the thickness of a solid deuterium
target measured using electron scattering
References
[1] Frank, A. et al., Energy loss of argon in a laser-generated
carbon plasma, Phys. Rev. E 81, 026401 2010
[2] Menzel, J., Setup and commissioning of a cryogenic system
for the production of targets to be used in experiments with
high energy lasers and heavy ion beams, Dissertation 2009
[3] Bagnoud, V. et al., Commissioning and early experiments of
the PHELIX facility, Appl Phys B, 2009
PLASMA-PHYSICS-07 GSI SCIENTIFIC REPORT 2009
392