Download ORION laser target diagnostics

ORION laser target diagnostics
C. D. Bentley, R. D. Edwards, J. E. Andrew, S. F. James, M. D. Gardner et al.
Citation: Rev. Sci. Instrum. 83, 10D732 (2012); doi: 10.1063/1.4748850
View online: http://dx.doi.org/10.1063/1.4748850
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REVIEW OF SCIENTIFIC INSTRUMENTS 83, 10D732 (2012)
ORION laser target diagnosticsa)
C. D. Bentley,b) R. D. Edwards, J. E. Andrew, S. F. James, M. D. Gardner, A. J. Comley,
K. Vaughan, C. J. Horsfield, M. S. Rubery, S. D. Rothman, S. Daykin, S. J. Masoero,
J. B. Palmer, A. L. Meadowcroft, B. M. Williams, E. T. Gumbrell, J. D. Fyrth, C. R. D. Brown,
M. P. Hill, K. Oades, M. J. Wright, B. A. Hood, and P. Kemshall
Plasma Physics Department, Atomic Weapons Establishment, Aldermaston, Reading,
Berkshire RG7 4PR, England
(Presented 9 May 2012; received 3 May 2012; accepted 3 June 2012;
published online 11 September 2012)
The ORION laser facility is one of the UK’s premier laser facilities which became operational at
AWE in 2010. Its primary mission is one of stockpile stewardship, ORION will extend the UK’s experimental plasma physics capability to the high temperature, high density regime relevant to Atomic
Weapons Establishment’s (AWE) program. The ORION laser combines ten laser beams operating in
the ns regime with two sub ps short pulse chirped pulse amplification beams. This gives the UK a
unique combined long pulse/short pulse laser capability which is not only available to AWE personnel but also gives access to our international partners and visiting UK academia. The ORION laser
facility is equipped with a comprehensive suite of some 45 diagnostics covering optical, particle, and
x-ray diagnostics all able to image the laser target interaction point. This paper focuses on a small
selection of these diagnostics. [http://dx.doi.org/10.1063/1.4748850]
I. INTRODUCTION
II. X-RAY DIAGNOSTICS
The ORION laser facility has been designed to provide
a world class high-energy density physics platform to help
support Atomic Weapons Establishment’s (AWE) primary
mission of stockpile stewardship. This new facility will be
available to both the AWE and academic scientific communities for fundamental research accessing new and exciting
physics regimes.
The ORION laser combines ten long pulse laser beams
operating in the nanosecond regime with two short pulse sub
picosecond chirped pulse amplification beams. The long pulse
beams are capable of delivering up to 500 J at 351 nm in a 1
ns square-pulse while the short pulse beams will both be capable of delivering 500 J at 1053 nm in a 0.5 ps pulse. This
combination of long and short pulse lasers will allow experimentalists to access new temperature and density domains.
Novel scientific opportunities such as high density and temperature material properties, high density plasma effects, xray heated plasmas in Hohlraums, short pulse physics, etc.,
will be investigated by utilising this facility.
Experimentalists using the ORION laser facility will
have a suite of 45 x-ray, optical, and particle diagnostics available to help diagnose the plasma conditions within the target
chamber. The ORION target chamber is fitted with Laboratory for Laser Energetics standard ten inch manipulator (TIM)
diagnostic inserters allowing the fielding of the diagnostics.
This paper will provide an overview of several of the diagnostics.
ORION has numerous x-ray sensitive detectors and diagnostics at its disposal. Between them these detectors cover
the spectral energy range from the ultraviolet (sub keV)
to hard x-ray and gamma energies (∼20 MeV). These include the filter fluorescer diagnostic, a number of spectrometers – twin crystal, precision optical spectrometer, transmission grating, x-ray ultraviolet grating, time integrated,
transmission cystal and hard x ray, a gated x-ray detector pinhole camera array, multi and single channel x-ray
pinhole cameras, high-energy x-ray spectrometer with interchangeable detectors (HEXID), gamma and Laue cameras, Dante/photoconductive detectors (PCDs) arrays, KB
x-ray microscope, gated x-ray detector, x-ray streak cameras
with cystal spectrometers and imaging snout, thermoluminescent dosimeter array, and a broad band x-ray diffraction diagnostic. In the following paragraphs brief descriptions are
given for a selection of these diagnostics.
a) Contributed paper, published as part of the Proceedings of the 19th
Topical Conference on High-Temperature Plasma Diagnostics, Monterey,
California, May 2012.
b) Author to whom correspondence should be addressed. Electronic mail:
[email protected].
0034-6748/2012/83(10)/10D732/3/$30.00
A. Filter flourescer diagnostic
The filter fluorescer diagnostic (FFLEX) (Figure 1) is an
absolute time-integrated hard x-ray spectrum diagnostic covering the energy range 20 keV to 100 keV. It is used to measure the x-ray emission of a laser irradiated target and thus
determine its temperature. Eight channels are used to measure
the hard x-rays produced by propagation of hot electrons generated via collisionless absorption at the laser-target boundary
in the target material.
Each channel consists of pre- and post-filters1 combined
with a fluorescer to define the spectral window for the channel. The x rays are detected by a photomultiplier tube coupled
with a NaI scintillator to produce a signal that is recorded by
an oscilloscope. Scattered high-energy radiation is mitigated
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Bentley et al.
Rev. Sci. Instrum. 83, 10D732 (2012)
2000
Ch1: CsAP (001) f=166.2 mm
Ch2: Quartz (10-10)
Ch3: Silicon (111)
Ch4: Germanium (220)
Ch1: CsAP (001) f=139.2 mm
Ch2: Qz (10-10)
Ch3: Si (111)
Ch4: Ge (220)
Resolving Power R
1800
1600
1400
1200
1000
800
600
400
200
0
1
2
3
4
5
6
7
8
9
10
X-ray energy E (keV)
FIG. 3. Resolving power obtained from each of the four channels at two
different focal lengths.
FIG. 1. The 8 channel detector head assembly.
by using filters, lead shielding, and specific scintillator thicknesses.
B. High energy resolution x-ray spectrometer
with interchangeable detectors
In recent years multi-channel spectrometers2, 3 have
been developed to measure the soft x-ray spectrum from
laser produced plasmas. The high energy resolution xray spectrometer with interchangeable detectors (HEX-ID)
(Figure 2) is a further progression of these diagnostics which
takes advantage of advances in x-ray detection technology.
It comprises four channels consisting of a combination of a
filter, a crystal, and a detector. This enables the diagnostic to
cover a spectral range of 1 to 10 keV with a resolution of E/dE
∼ 800 (Figure 3). The diagnostic has a range of interchangeable x-ray detectors with which it can be fielded, these being
image plates, CMOS x-ray sensors, and PCDs. The selection
of detector is dependent on the desired dynamic range, spatial,
and temporal resolutions. The HEX-ID is a TIM deployed diagnostic for use with long pulse and short pulse laser shots.
C. Dante diagnostic
For the ORION project a Dante diagnostic (Figure 4) has
been designed for use in measuring time resolved laser plasma
target temperatures. This is achieved through the measure-
FIG. 2. CAD drawing depicting the HEXID assembly and airbox containing
control and data acquisition electronics.
ment of low energy (<2 keV) x rays emitted from long pulse
laser interactions. The design of the diagnostic has incorporated the capability to extend the measurement spectral range
to 4 keV.
The diagnostic is comprised of ten channels with the option for up to a further eight to be added at a later date. Each
channel consists of a filter and x-ray diode (XRD) combination which define the spectral range of each channel. Several of these channels also incorporate a mirror assembly to
further define the spectral range covered by these channels.
A new XRD (known as the DiABLO) has been designed
(Figure 5) which is based on the XRD’s used in the Dante
diagnostic for ORION’s predecessor laser facility – HELEN.
This detector has been designed to operate inside a
vacuum and incorporates a larger photocathode and modern
high voltage and signal connectors. The XRD, filters, and
mirrors have all been absolutely characterised using the
characterisation beamlines at the National Synchrotron Light
Source at the Brookhaven National Laboratories.4
III. OPTICAL DIAGNOSTICS
The ORION laser facility has a comprehensive suite of
optical diagnostics (Figure 6) consisting of passive shock
breakout (PaSBO), active shock breakout (ASBO), velocity
interferometer from the surface of any reflector (VISAR),
probe beam detector, streaked optical pyrometry (SOP), full
aperture SRS/SBS backscatter, and long and short pulse near
backscatter imagers. These are used to provide measurements
of various materials in a warm dense matter state (ρ ∼
solid, T ∼0.1–10 eV). Temperature, density, shock speed, and
FIG. 4. Schematic of the ORION Dante diagnostic.
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10D732-3
Bentley et al.
Al, N
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carrier
Rev. Sci. Instrum. 83, 10D732 (2012)
Taper ed 50Ω
Tapered
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50
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ssiion lline
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SMA
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FIG. 7. Outline schematic of ORION electron spectrometer.
can also be used as single-colour reflectivity diagnostics to aid
in pyrometry.7, 10
FIG. 5. Schematic of the DiABLO XRD.
emissivity are all properties which can be measured optically
to characterise the target plasma.
A. Fast probing and tomography – Short pulse probes
ORION is equipped with two <0.5 ps, 100 mJ, 4
(264 nm), polarization controlled probe beams derived from
the main short pulse system. These can be used for deep-UV
reflectivity (Pyrometry), axial and tomographic electron density probing (hohlraums), pre-plasma diagnosis, and sheath
field/target surface manipulation.
B. Passive imaging – SOP and PaSBO
SOP and PaSBO have been used to measure the selfemission from targets to determine temperature5–7 and shock
speed8, 9 without the use of a probe laser. Pyrometry is however greatly enhanced by the use of an active reflectivity
probe to correct for the imperfect blackbody nature of the
plasma.7, 10
IV. PARTICLE DIAGNOSTICS
ORION has several particle diagnostics which include
neutron total yield, CR39, Faraday cups system, low energy
electron spectrometer/EPPS, EMP detector, neutron time of
flight, thomson parabola, radiochromic film, electron spectrometer, proton/ion magnetic spectrometer, and the SGEMP
Cavity. The electron spectrometer is discussed in further detail below.
A. Electron spectrometer
ORION’s electron spectrometer (Figure 7) is
designed13–15 to cover the electron spectrum from 50 MeV
to 1 GeV and utilises a magnetic field to deflect electrons.
The electron interaction produces x rays which are recorded
on the image plate along with Brehmsstrhalung radiation.
Processing the data to remove the background and taking
lineouts across the image plate allows us to infer the electron
spectrum.
ACKNOWLEDGMENTS
C. Active probing – VISAR and ASBO
VISAR and ASBO are two well established optical diagnostics for monitoring the expansion of a plasma and/or the
propagation of a shock through a target.11, 12 If calibrated they
Use of the National Synchrotron Light Source,
Brookhaven National Laboratory, was supported by the U.S.
Department of Energy, Office of Science, Office of Basic
Energy Sciences, under Contract No. DE-AC02-98CH10886.
1 H.
Target material
being measured
Probe laser
Beam-splitter
TIM-mounted
diagnostics
front-end(s)
Light coming-off
the target, either
self-emitted or
probe beam
Down-stream
optics & lens
group(s) for
transport and
re-imaging
Optical streak camera group
(up to 7 cameras)
Streaked optical pyrometry (also
Green or IR reflectivity probe )
PaSBO (no
probe laser)
ASBO
(Green or IR probe)
Objective
(& other TIM
optics)
VISAR (Green probe,
upgradeable to IR probe)
* Excluding short-pulse probes or back-scatter diagnostics
FIG. 6. Outline schematic of ORION optical diagnostics.
N. Kornblum et al., “Filter fluorescer experiment on the Argus laser,”
LLNL Internal Report, September 1978.
2 L. N. Koppel and J. D. Eckels, “High resolution x-ray crystal spectrographs,” LLNL Report UCRL-79781, 1977.
3 J. Seely et al., “Hard x-ray spectrometers for the national ignition facility,”
Rev. Sci. Instrum. 72(6), 2562–2565 (2001).
4 C. D. Bentley and A. C. Simmons, Rev. Sci. Instrum. 72, 1202 (2001).
5 N. C. Holmes et al., Rev. Sci. Instrum. 66, 2615 (1995).
6 J. E. Miller et al., Rev. Sci. Instrum. 78, 034903 (2007).
7 A. N. Mostovych and Y. Chan, Rev. Lett. 79(25), 5094 (1997).
8 A. Ng et al., Phys. Rev. Lett. 54(24), 2604 (1985).
9 S. D. Rothman et al., Phys. Plasmas 9(5), 1721 (2002).
10 T. Sano et al., Phys. Rev. B 83, 054117 (2011).
11 G. W. Collins et al., Science 281, 1178 (1998).
12 P. M. Celliers et al., Rev. Sci. Instrum. 75, 4916 (2004).
13 M Zepf et al., “Fast particle generation and energy transport in laser-solid
interactions,” Phys. Plasmas 8(5), 175001 (2001).
14 M Tatarakis et al., “Propagation instabilities of high-intensity laserproduced electron beams,” Phys. Rev. Lett. 90(17), 2323 (2003).
15 H. Chen et al., “Short pulse laser produced energetic electron and positron
measurements,” Rev. Sci. Instrum. 77(10), 10E703 (2006).
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