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May 2008

Volume 79, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 79, 051301 (2008); http://dx.doi.org/10.1063/1.2919944 (12 pages)

C. R. Locke, E. N. Ivanov, J. G. Hartnett, P. L. Stanwix, and M. E. Tobar

Top view of a false colored image of the electric field density in a whispering gallery mode with 16 azimuthal variations. The sapphire cylinder is not shown, but its outer circumference is defined by the total internal reflection within the crystal—close to the outer edge of the red petals.

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Invited Article: Design techniques and noise properties of ultrastable cryogenically cooled sapphire-dielectric resonator oscillators

C. R. Locke, E. N. Ivanov, J. G. Hartnett, P. L. Stanwix, and M. E. Tobar

Rev. Sci. Instrum. 79, 051301 (2008); http://dx.doi.org/10.1063/1.2919944 (12 pages) | Cited 14 times

Online Publication Date: 12 May 2008

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We review the techniques used in the design and construction of cryogenic sapphire oscillators at the University of Western Australia over the 18 year history of the project. We describe the project from its beginnings when sapphire oscillators were first developed as low-noise transducers for gravitational wave detection. Specifically, we describe the techniques that were applied to the construction of an interrogation oscillator for the PHARAO Cs atomic clock in CNES, in Toulouse France, and to the 2006 construction of four high performance oscillators for use at NMIJ and NICT, in Japan, as well as a permanent secondary frequency standard for the laboratory at UWA. Fractional-frequency fluctuations below 6×10−16 at integration times between 10 and 200 s have been repeatedly achieved.
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07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
84.40.-x Radiowave and microwave (including millimeter wave) technology
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A versatile all-optical Bose–Einstein condensates apparatus

Y. C. Wenas and M. D. Hoogerland

Rev. Sci. Instrum. 79, 053101 (2008); http://dx.doi.org/10.1063/1.2917405 (5 pages) | Cited 2 times

Online Publication Date: 6 May 2008

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We report on the construction of an all-optical Bose–Einstein condensate apparatus by using a CO2 laser trap. We also report on measurements of the trap frequency by applying a periodic perturbation to the trap potential. The derived trap parameters agree well with the design parameters.
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37.10.Gh Atom traps and guides
32.80.-t Photoionization and excitation

A subnanosecond pulsed ion source for micrometer focused ion beams

C. Höhr, D. Fischer, R. Moshammer, A. Dorn, and J. Ullrich

Rev. Sci. Instrum. 79, 053102 (2008); http://dx.doi.org/10.1063/1.2918136 (6 pages)

Online Publication Date: 6 May 2008

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A new, compact design of an ion source delivers nanosecond pulsed ion beams with low emittance, which can be focused to micrometer size. By using a high-power, 25 fs laser pulse focused into a gas region of 10−6 mbar, ions at very low temperatures are produced in the small laser focal volume of 5 μm diameter by 20 μm length through multiphoton ionization. These ions are created in a cold environment, not in a hot plasma, and, since the ionization process itself does not significantly heat them, have as a result essentially room temperature. The generated ion pulse, up to several thousand ions per pulse, is extracted from the source volume with ion optical elements that have been carefully designed by simulation calculations. Externally triggered, its subnanosecond duration and even smaller time jitter allow it to be superimposed with other pulsed particle or laser beams. It therefore can be combined with any type of collision experiment where the size and the time structure of the projectile beam crucially affect the achievable experimental resolution.
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07.77.Ka Charged-particle beam sources and detectors
29.25.Ni Ion sources: positive and negative
41.75.-i Charged-particle beams

A broadband Fourier transform microwave spectrometer based on chirped pulse excitation

Gordon G. Brown, Brian C. Dian, Kevin O. Douglass, Scott M. Geyer, Steven T. Shipman, and Brooks H. Pate

Rev. Sci. Instrum. 79, 053103 (2008); http://dx.doi.org/10.1063/1.2919120 (13 pages) | Cited 36 times

Online Publication Date: 9 May 2008

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Designs for a broadband chirped pulse Fourier transform microwave (CP-FTMW) spectrometer are presented. The spectrometer is capable of measuring the 7–18 GHz region of a rotational spectrum in a single data acquisition. One design uses a 4.2 Gsamples/s arbitrary waveform generator (AWG) to produce a 1 μs duration chirped pulse with a linear frequency sweep of 1.375 GHz. This pulse is sent through a microwave circuit to multiply the bandwidth of the pulse by a factor of 8 and upconvert it to the 7.5–18.5 GHz range. The chirped pulse is amplified by a traveling wave tube amplifier and broadcast inside the spectrometer by using a double ridge standard gain horn antenna. The broadband molecular free induction decay (FID) is received by a second horn antenna, downconverted, and digitized by a 40 Gsamples/s (12 GHz hardware bandwidth) digital oscilloscope. The second design uses a simplified pulse generation and FID detection scheme, employing current state-of-the-art high-speed digital electronics. In this spectrometer, a chirped pulse with 12 GHz of bandwidth is directly generated by using a 20 Gsamples/s AWG and upconverted in a single step with an ultrabroadband mixer. The amplified molecular emission is directly detected by using a 50 Gsamples/s digital oscilloscope with 18 GHz bandwidth. In both designs, fast Fourier transform of the FID produces the frequency domain rotational spectrum in the 7–18 GHz range. The performance of the CP-FTMW spectrometer is compared to a Balle–Flygare–type cavity-FTMW spectrometer. The CP-FTMW spectrometer produces an equal sensitivity spectrum with a factor of 40 reduction in measurement time and a reduction in sample consumption by a factor of 20. The CP-FTMW spectrometer also displays good intensity accuracy for both sample number density and rotational transition moment. Strategies to reduce the CP-FTMW measurement time by another factor of 90 while simultaneously reducing the sample consumption by a factor of 30 are demonstrated.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

Wedged multilayer Laue lens

Ray Conley, Chian Liu, Jun Qian, Cameron M. Kewish, Albert T. Macrander, Hanfei Yan, Hyon Chol Kang, Jörg Maser, and G. Brian Stephenson

Rev. Sci. Instrum. 79, 053104 (2008); http://dx.doi.org/10.1063/1.2924209 (4 pages) | Cited 7 times

Online Publication Date: 14 May 2008

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A multilayer Laue lens (MLL) is an x-ray focusing optic fabricated from a multilayer structure consisting of thousands of layers of two different materials produced by thin-film deposition. The sequence of layer thicknesses is controlled to satisfy the Fresnel zone plate law and the multilayer is sectioned to form the optic. An improved MLL geometry can be created by growing each layer with an in-plane thickness gradient to form a wedge, so that every interface makes the correct angle with the incident beam for symmetric Bragg diffraction. The ultimate hard x-ray focusing performance of a wedged MLL has been predicted to be significantly better than that of a nonwedged MLL, giving subnanometer resolution with high efficiency. Here, we describe a method to deposit the multilayer structure needed for an ideal wedged MLL and report our initial deposition results to produce these structures.
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07.85.-m X- and γ-ray instruments
81.15.Cd Deposition by sputtering
68.65.Ac Multilayers

Optical fiber sensor for small angle and infinite angle detection

Tao Lü, Xianli Lang, and Yanling Han

Rev. Sci. Instrum. 79, 053105 (2008); http://dx.doi.org/10.1063/1.2929674 (5 pages) | Cited 1 time

Online Publication Date: 19 May 2008

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An optical fiber angle sensor that consists of a cam, linear displacement attenuators, and a sensitive Fabry–Pérot cavity (FPC), is demonstrated to simultaneously measure small angle and infinite angle with high resolution. When the cam is driven to rotate by a fixed rotary shaft, a linear displacement transformed from an angle will be further attenuated by linear displacement attenuators and will subsequently modulate the FPC, which causes the reflected interference intensity of FPC to vary. By using the method of interferometric fringe counting, we can measure an infinite angle accurately and continuously. Moreover, a small angle measurement can be performed in a locally linear region. Experimental results show that two resolutions of 0.5 and 1.5 s in the angle range of 0.1944° and 3.5496° are achieved, respectively.
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42.81.Pa Sensors, gyros
42.79.-e Optical elements, devices, and systems
07.60.Ly Interferometers

A synthetic heterodyne interferometer for small amplitude of vibration measurement

Seonggu Kang, Jongpil La, Heesun Yoon, and Kyihwan Park

Rev. Sci. Instrum. 79, 053106 (2008); http://dx.doi.org/10.1063/1.2936256 (6 pages)

Online Publication Date: 30 May 2008

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The homodyne interferometer has the advantages of simple optical configuration and low cost. However, it requires a caution in using an electronic filter such as high pass filter (HPF) to get rid of low frequency electronic noises and the dc offset associated with the optical intensity in the photodiode electronic circuitry. When the vibration amplitude is smaller than at least 1/2 of the wavelength of He–Ne laser, a problem of incorrect velocity or distorted velocity measurement can be caused since a dc value of the interference signal is eliminated by using the HPF. To solve this problem of using the HPF in the homodyne interferometer, a synthetic interferometer using a mechanical modulation method is proposed in this work by exciting a reference mirror with the displacement larger than 1/2 of the wavelength. In this work, the analytical work is presented to show how the synthetic interferometer solves the problem of incorrect velocity measurement by using the Fourier–Bessel function description of the interference signals. Simulation and experimental works are also presented to validate the synthetic heterodyne interferometer proposed in this work.
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43.58.+z Acoustical measurements and instrumentation
43.60.+d Acoustic signal processing
42.79.Jq Acousto-optical devices
07.60.Ly Interferometers
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Broadband single-shot electron spectrometer for GeV-class laser-plasma-based accelerators

K. Nakamura, W. Wan, N. Ybarrolaza, D. Syversrud, J. Wallig, and W. P. Leemans

Rev. Sci. Instrum. 79, 053301 (2008); http://dx.doi.org/10.1063/1.2929672 (5 pages) | Cited 10 times

Online Publication Date: 20 May 2008

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Laser-plasma-based accelerators can provide electrons over a broad energy range and/or with large momentum spread. The electron beam energy distribution can be controlled via accurate control of laser and plasma properties, and beams with energies ranging from ≃ 0.5 to 1000 MeV have been observed. Measuring these energy distributions in a single shot requires the use of a diagnostic with large momentum acceptance and, ideally, sufficient resolution to accurately measure narrow energy spread beams. Such a broadband single-shot electron magnetic spectrometer for GeV-class laser-plasma-based accelerators has been developed at Lawrence Berkeley National Laboratory. Detailed descriptions of the design concept and hardware are presented, as well as a performance evaluation of the spectrometer. The spectrometer covered electron beam energies raging from 0.01 to 1.1 GeV in a single shot, and enabled the simultaneous measurement of the laser properties at the exit of the accelerator through the use of a sufficiently large pole gap. Based on measured field maps and third-order transport analysis, a few percent-level resolution and determination of the absolute energy were achieved over the entire energy range. Laser-plasma-based accelerator experiments demonstrated the capability of the spectrometer as a diagnostic and its suitability for measuring broadband electron sources.
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07.81.+a Electron and ion spectrometers
29.30.Aj Charged-particle spectrometers: electric and magnetic
29.30.Ep Charged-particle spectroscopy
52.38.Kd Laser-plasma acceleration of electrons and ions
29.20.Ej Linear accelerators
41.75.Fr Electron and positron beams
29.27.Fh Beam characteristics

Sub-MeV tunably polarized X-ray production with laser Thomson backscattering

K. Kawase, M. Kando, T. Hayakawa, I. Daito, S. Kondo, T. Homma, T. Kameshima, H. Kotaki, L.-M. Chen, Y. Fukuda, A. Faenov, T. Shizuma, M. Fujiwara, S. V. Bulanov, T. Kimura, et al.

Rev. Sci. Instrum. 79, 053302 (2008); http://dx.doi.org/10.1063/1.2931010 (8 pages) | Cited 7 times

Online Publication Date: 22 May 2008

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Reported in this article is the generation of unique polarized x-rays in the sub-MeV region by means of the Thomson backscattering of the Nd:YAG laser photon with a wavelength of 1064 nm on the 150 MeV electron from the microtron accelerator. The maximum energy of the x-ray photons is estimated to be about 400 keV. The total energy of the backscattered x-ray pulse is measured with an imaging plate and a LYSO scintillator. The angular divergence of the x-rays is also measured by using the imaging plate. We confirm that the x-ray beam is polarized according to the laser polarization direction with the Compton scattering method. In addition, we demonstrate the imaging of the object shielded by lead with the generated x-rays.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
42.62.-b Laser applications
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Use of GafChromic film to diagnose laser generated proton beams

D. S. Hey, M. H. Key, A. J. Mackinnon, A. G. MacPhee, P. K. Patel, R. R. Freeman, L. D. Van Woerkom, and C. M. Castaneda

Rev. Sci. Instrum. 79, 053501 (2008); http://dx.doi.org/10.1063/1.2901603 (4 pages) | Cited 9 times

Online Publication Date: 8 May 2008

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A calibration of three types of GafChromic radiochromic film (HS, MD-55, and HD-810) was carried out on the Crocker Nuclear Laboratory’s 76 in. cyclotron at UC Davis over doses ranging from 0.001 to 15 kGy. The film was digitized with a scanning microdensitometer with which it was scanned twice with two different filters to increase the film’s effective dynamic range. We demonstrate how this calibrated film can be used to measure the spectrum and total energy of a laser generated proton beam. This technique was applied to an experiment on the 10 J, 100 fs Callisto laser at Lawrence Livermore National Laboratory. The resulting proton spectrum was compared to that obtained by simultaneous measurement of Ti nuclear activation; the two methods give the same proton beam slope temperature and agree in number of protons to within 27%.
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29.25.Ni Ion sources: positive and negative

Preparation of ortho-para ratio controlled D2 gas for muon-catalyzed fusion

H. Imao, K. Ishida, N. Kawamura, T. Matsuzaki, Y. Matsuda, A. Toyoda, P. Strasser, M. Iwasaki, and K. Nagamine

Rev. Sci. Instrum. 79, 053502 (2008); http://dx.doi.org/10.1063/1.2918538 (10 pages) | Cited 1 time

Online Publication Date: 9 May 2008

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A negative muon in hydrogen targets, e.g., D2 or D–T mixture, can catalyze nuclear fusions following a series of atomic processes involving muonic hydrogen molecular formation (muon-catalyzed fusion, μCF). The ortho-para state of D2 is a crucial parameter not only for enhancing the fusion rate but also to precisely investigate various muonic atom processes. We have developed a system for controlling and measuring the ortho-para ratio of D2 gas for μCF experiments. We successfully collected para-enriched D2 without using liquid-hydrogen coolant. Ortho-enriched D2 was also obtained by using a catalytic conversion method with a mixture of chromium oxide and alumina. The ortho-para ratio of D2 gas was measured with a compact Raman spectroscopy system. We produced large volume (5–30 l at STP), high-purity (less than ppm high-Z contaminant) D2 targets with a wide range of ortho-para ratios (ortho 20%–99%). By using the ortho-para controlled D2 in μCF experiments, we observed the dependence of μCF phenomena on the ortho-para ratio.
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25.30.Mr Muon-induced reactions (including the EMC effect)

Unfolding core asymmetries with x-ray emission images in symmetry diagnostic experiments

T. X. Huang, Y. K. Ding, Z. J. Zheng, W. Y. Miao, Z. R. Cao, S. E. Jiang, S. Y. Liu, and Z. L. Liu

Rev. Sci. Instrum. 79, 053503 (2008); http://dx.doi.org/10.1063/1.2924212 (3 pages)

Online Publication Date: 14 May 2008

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A novel inversion technique is proposed to unfold core asymmetries at the source with x-ray emission images, which were obtained from imploded surrogate capsules in symmetry diagnostic experiments. The axisymmetrical core emission can be expanded as a Fourier series, with Legendre polynomials and spherical Bessel functions as bases concerned with polar angle and radius, respectively. A least-squares estimator is employed to obtain the unknown coefficients from its two-dimensional image data. The unfolded Legendre coefficients can be further used to test modeling of drive asymmetries in hohlraums. This technique is also demonstrated with a proof-of-principle experiment performed on the Shenguang II laser facility [ L. Zunqi et al., Chin. J. Lasers B10, 6 (2001) ].
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52.70.La X-ray and γ-ray measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Three-electrode gas switches with electrodynamical acceleration of a discharge channel

B. M. Kovalchuk, A. A. Kim, A. V. Kharlov, E. V. Kumpyak, N. V. Tsoy, V. V. Vizir, and V. B. Zorin

Rev. Sci. Instrum. 79, 053504 (2008); http://dx.doi.org/10.1063/1.2929670 (6 pages) | Cited 2 times

Online Publication Date: 20 May 2008

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High voltage, high current, and high Coulomb transfer closing switches are required for many high power pulsed systems. There are a few alternatives for closing switches, for example, ignitrons, vacuum switches, solid-state switches, high pressure gas switches (spark gaps), and some others. The most popular closing switches up to date are spark gaps due to relatively simple design, robustness, easily field maintenance, and repair. Main drawback of spark gaps is limited lifetime, which is related directly or indirectly to erosion of the electrodes. Multichannel switches and switches with moving arc have been proposed to prevent the electrodes erosion. This study investigates switches, where a spark channel is initiated in a three-electrode layout and then the spark accelerates due to electrodynamic force and moves along the extended electrodes. At a given current amplitude, the diameter of the extended electrodes allows to control the spark velocity and hence, the erosion of the electrodes providing the required lifetime. The first switch is designed for 24 kV charging voltage and ∼ 4 C total charge transfer. This spark gap was tested at 25 kA peak current in 40 000 shots in a single polarity discharge and in 20 000 shots in bipolar discharge. Second spark gap is designed for 24 kV charging voltage and ∼ 70 C total charge transfer. It was tested in 22 000 shots, at a current of 250 kA with a pulse length of 360 μs. In this paper, we present design of these spark gaps and trigger generator, describe the test bed, and present the results of the tests.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity

A compact, multiangle electron spectrometer for ultraintense laser-plasma interaction experiments

O. V. Gotchev, P. Brijesh, P. M. Nilson, C. Stoeckl, and D. D. Meyerhofer

Rev. Sci. Instrum. 79, 053505 (2008); http://dx.doi.org/10.1063/1.2917879 (8 pages)

Online Publication Date: 22 May 2008

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Experiments on the multiterawatt (MTW) laser at the Laboratory for Laser Energetics will study the effect of the focal-spot shape on the forward acceleration and collimation of electrons. A compact electron spectrometer has been developed to record the energy spectra of electrons ejected in the interaction of the laser at multiple angular locations simultaneously. The modular system with replaceable magnets provides an adjustable energy band, currently 0.2–6 MeV. The detector is an array of imaging plates. The device is designed to operate in the high-noise environment (bremsstrahlung and Compton x rays, gamma rays, and scattered electrons), while being compact enough to fit in the 30 cm radius MTW target chamber. The detector geometry and shielding were optimized with the particle/radiation transport code GEANT4. Calibration was performed with beta sources. The required dynamic range, sensitivity, and resolution were confirmed with initial MTW experimental data.
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52.38.Dx Laser light absorption in plasmas (collisional, parametric, etc.)
52.25.Fi Transport properties
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.La X-ray and γ-ray measurements
52.70.Nc Particle measurements
52.50.Dg Plasma sources

Measurement of derivative of ion temperature using high spatial resolution charge exchange spectroscopy with space modulation optics

K. Ida, Y. Sakamoto, M. Yoshinuma, S. Inagaki, T. Kobuchi, G. Matsunaga, and Y. Koide

Rev. Sci. Instrum. 79, 053506 (2008); http://dx.doi.org/10.1063/1.2921702 (6 pages) | Cited 8 times

Online Publication Date: 23 May 2008

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A new technique to measure the first and second derivatives of the ion temperature profile has been developed by using a charge exchange spectroscopy system with space modulation optics. The space observed is scanned up to ±3 cm with a cosine wave modulation frequency up to 30 Hz by shifting the object lens in front of the optical fiber bundle by 0.5 mm with a piezoelement. The first and second derivatives of ion temperature are derived from the modulation component of the ion temperature measured by using Fourier series expansion.
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52.25.Kn Thermodynamics of plasmas
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
34.70.+e Charge transfer
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Quantitative imaging of Young’s modulus of solids: A contact-mechanics study

H. Ogi, T. Inoue, H. Nagai, and M. Hirao

Rev. Sci. Instrum. 79, 053701 (2008); http://dx.doi.org/10.1063/1.2908437 (8 pages) | Cited 2 times

Online Publication Date: 15 May 2008

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We developed equipment and methods for measuring quantitatively the local Young’s modulus of solids. It consists of an electrodeless langasite oscillator and line antennas, and oscillator vibrations are generated and detected contactlessly. A constant biasing force results from oscillator mass and is independent of surface roughness. The effect of material anisotropy on the measured stiffness is theoretically discussed for studying the limitation of the quantitative measurement. The microscopy has been applied to polycrystalline copper, and the measured modulus is compared to calculations based on electron-backscatter-diffraction measurements. Also, we applied it to a duplex stainless steel and an embedded silicon-carbide fiber. The results reveal textured regions, defects with high sensitivity, and even stiffness distribution in a single grain.
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46.80.+j Measurement methods and techniques in continuum mechanics of solids
46.25.-y Static elasticity
46.40.-f Vibrations and mechanical waves
46.55.+d Tribology and mechanical contacts
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli

Development of a momentum microscope for time resolved band structure imaging

B. Krömker, M. Escher, D. Funnemann, D. Hartung, H. Engelhard, and J. Kirschner

Rev. Sci. Instrum. 79, 053702 (2008); http://dx.doi.org/10.1063/1.2918133 (7 pages) | Cited 7 times

Online Publication Date: 19 May 2008

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We demonstrate the use of a novel design of a photoelectron microscope in combination to an imaging energy filter for momentum resolved photoelectron detection. Together with a time resolved imaging detector, it is possible to combine spatial, momentum, energy, and time resolution of photoelectrons within the same instrument. The time resolution of this type of energy analyzer can be reduced to below 100 ps. The complete ARUPS pattern of a Cu(111) sample excited with He I, is imaged in parallel and energy resolved up to the photoelectron emission horizon. Excited with a mercury light source (hν = 4.9 eV), the Shockley surface state at the energy threshold is clearly imaged in k-space. Electron-electron interactions are observed in momentum space as a correlation hole in two-electron photoemission. With the high transmission and the time resolution of this instrument, possible new measurements are discussed: Time and polarization resolved ARUPS measurements, probing change of bandstructure due to chemical reaction, growth of films, or phase transitions, e.g., melting or martensitic transformations.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.47.D- Time resolved spectroscopy (>1 psec)

Design, fabrication, and characterization of diffraction gratings for neutron phase contrast imaging

C. Grünzweig, F. Pfeiffer, O. Bunk, T. Donath, G. Kühne, G. Frei, M. Dierolf, and C. David

Rev. Sci. Instrum. 79, 053703 (2008); http://dx.doi.org/10.1063/1.2930866 (6 pages) | Cited 14 times

Online Publication Date: 23 May 2008

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We have developed a neutron phase contrast imaging method based on a grating interferometer setup. The principal constituents are two absorption gratings made of gadolinium and a phase modulating grating made of silicon. The design parameters of the setup, such as periodicity, structure heights of the gratings, and the distances between the gratings, are calculated. The fabrication of each grating is described in detail. The produced diffraction gratings were finally characterized within the setup, by locally evaluating the produced contrast (visibility) in each detector pixel, resulting in a visibility map over the whole grating size. An averaged value of 23% is achieved.
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03.75.Dg Atom and neutron interferometry
03.75.Be Atom and neutron optics
42.79.Dj Gratings
42.15.Eq Optical system design

Gradiometric micro-SQUID susceptometer for scanning measurements of mesoscopic samples

Martin E. Huber, Nicholas C. Koshnick, Hendrik Bluhm, Leonard J. Archuleta, Tommy Azua, Per G. Björnsson, Brian W. Gardner, Sean T. Halloran, Erik A. Lucero, and Kathryn A. Moler

Rev. Sci. Instrum. 79, 053704 (2008); http://dx.doi.org/10.1063/1.2932341 (7 pages) | Cited 19 times

Online Publication Date: 28 May 2008

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We have fabricated and characterized micro-SQUID susceptometers for use in low-temperature scanning probe microscopy systems. The design features the following: a 4.6 μm diameter pickup loop; an integrated field coil to apply a local field to the sample; an additional counterwound pickup-loop/field-coil pair to cancel the background signal from the applied field in the absence of the sample; modulation coils to allow setting the SQUID at its optimum bias point (independent of the applied field), and shielding and symmetry that minimizes coupling of magnetic fields into the leads and body of the SQUID. We use a SQUID series array preamplifier to obtain a system bandwidth of 1 MHz. The flux noise at 125 mK is approximately 0.25μΦ0/math above 10 kHz, with a value of 2.5μΦ0/math at 10 Hz. The nominal sensitivity to electron spins located at the center of the pickup loop is approximately 200μB/math above 10 kHz, in the white-noise frequency region.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
04.80.Nn Gravitational wave detectors and experiments
84.30.Le Amplifiers
84.71.Ba Superconducting magnets; magnetic levitation devices
85.25.Cp Josephson devices
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Construction of a low-temperature thermodynamic measurement system for single crystal of molecular compounds under pressures

Osamu Kubota and Yasuhiro Nakazawa

Rev. Sci. Instrum. 79, 053901 (2008); http://dx.doi.org/10.1063/1.2912816 (6 pages) | Cited 5 times

Online Publication Date: 5 May 2008

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An apparatus to obtain low-temperature thermodynamic information under high pressures for a tiny single crystal of molecular compounds was developed based on the ac technique. To detect small temperature oscillation of a sample inside the cramp-type pressure cell, we have used a small ruthenium oxide chip sensor as a thermometer. The adoption of the four-terminal method by the ac resistance bridge has made high-resolution detection of thermal anomaly possible in the low-temperature region. The constructed high-pressure thermodynamic system was mounted on a 3He refrigerator and we have succeeded to detect the thermal anomaly in relevant to magnetic order of single crystal sample of Mn4-cluster complex up to 1.05 GPa. A distinct peak of the heat capacity and its upward shift with increasing pressures was observed using a tiny crystal of about 100 μg. The high-pressure behavior of the discontinuity of heat capacity at the superconductive transition of 6 mg of metal indium has also been detected by this apparatus. The details and performance of the technique are reported.
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65.40.Ba Heat capacity
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
74.62.-c Transition temperature variations, phase diagrams

Thermodynamic measurements of submilligram bulk samples using a membrane-based “calorimeter on a chip”

David W. Cooke, K. J. Michel, and F. Hellman

Rev. Sci. Instrum. 79, 053902 (2008); http://dx.doi.org/10.1063/1.2912950 (10 pages) | Cited 7 times

Online Publication Date: 6 May 2008

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Calorimetry offers a direct measurement of thermodynamic properties of materials, including information on the energetics of phase transitions. Many materials can only be prepared in thin film or small crystal (submilligram) form, negating the use of traditional bulk techniques. The use of micromachined, membrane-based calorimeters for submilligram bulk samples is detailed here. Numerical simulations of the heat flow for this use have been performed. These simulations describe the limits to which this calorimetric technique can be applied to the realm of small crystals (1–1000 μg). Experimental results confirm the feasibility of this application over a temperature range from 2 to 300 K. Limits on sample thermal conductivity as it relates to the application of the lumped and distributed τ2 models are explored. For a typical sample size, the simulations yield 2.5% absolute accuracy for the heat capacity of a sample with thermal conductivity as low as 2×10−5 W/cm K at 20 K, assuming a strong thermal link to the device. Silver paint is used to attach (both thermally and physically) the small samples; its heat capacity and reproducibility are discussed. Measurements taken of a submilligram single crystal of cobalt oxide (CoO) compare favorably to the results of a bulk calorimetric technique on a larger sample.
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65.40.Ba Heat capacity
07.20.Fw Calorimeters
66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.K- Solid-solid transitions

A cubic boron nitride gasket for diamond-anvil experiments

Nobumasa Funamori and Tomoko Sato

Rev. Sci. Instrum. 79, 053903 (2008); http://dx.doi.org/10.1063/1.2917409 (5 pages) | Cited 9 times

Online Publication Date: 13 May 2008

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To maximize the thickness of the sample chamber in high-pressure experiments, we have conducted tests and have developed techniques relevant to the cubic boron nitride (c-BN) gasket for diamond-anvil cells. The c-BN gasket provides a sample chamber several times thicker than conventional metal gaskets. We have developed methods to prepare the gasket and to fill the chamber with the sample. By using the c-BN gasket, we have successfully measured x-ray diffraction patterns of SiO2 glass, a low-Z noncrystalline sample, up to 100 GPa.
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61.43.Fs Glasses
61.72.Dd Experimental determination of defects by diffraction and scattering

The compact capacitor bank CQ-1.5 employed in magnetically driven isentropic compression and high velocity flyer plate experiments

Guiji Wang, Chengwei Sun, Fuli Tan, Jianheng Zhao, Ning Zhang, Cangli Liu, Jianjun Mo, Ganghua Wang, and Xiaosong Wang

Rev. Sci. Instrum. 79, 053904 (2008); http://dx.doi.org/10.1063/1.2920200 (6 pages)

Online Publication Date: 14 May 2008

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Based on the low inductance capacitor, the parallel-plate transmission line, and the explosive network closing switch, a compact pulsed power generator CQ-1.5 has been developed at the Institute of Fluid Physics and is capable to deliver a current of peak of 1.5 MA within rise time of 500–570 ns into a 2–3 nH inductive load. The work is motivated to do isentropic compression experiments (ICEs) on metals up to 30–50 GPa and to launch flyer plates at velocities over 8 km/s. The experiments were conducted with the diagnostics of both Doppler pin system and velocity interferometer system for any reflectors, and the measured free surface velocity histories of ICE samples were treated with a backward integration code. The results show that the isentropes of Cu and Al samples under 35 GPa are close to their Hugoniots within a deviation of 3%. The LY12 aluminum flyer plates were accelerated to a velocity over 8.96 km/s.
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81.70.Bt Mechanical testing, impact tests, static and dynamic loads
62.50.Ef Shock wave effects in solids and liquids

Experimental evidence of an incomplete thermalization of the energy in an x-ray microcalorimeter with a Ta/Au absorber

E. Perinati, M. Barbera, S. Varisco, E. Silver, J. Beeman, and C. Pigot

Rev. Sci. Instrum. 79, 053905 (2008); http://dx.doi.org/10.1063/1.2924211 (4 pages) | Cited 1 time

Online Publication Date: 15 May 2008

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We have conducted an experimental test at our XACT facility using an x-ray microcalorimeter with Ta/Au absorber and neutron transmutation doped germanium thermal sensor. The test was aimed at measuring the percentage of energy effectively thermalized after absorption of x-ray photons in superconducting tantalum. Moreover, in general, possible formation of long living quasiparticles implies that by using a superconducting absorber, a fraction of the deposited energy could not be thermalized on the useful time scale of the thermal sensor. To investigate this scenario, we exploited an absorber made of gold, where no energy trapping is expected, with a small piece of superconducting tantalum attached on top. We obtained evidence that the thermalization of photons absorbed in tantalum is delayed by energy trapping from quasiparticles. We compare the experimental results with numerical simulations and derive a value for the intrinsic lifetime of quasiparticles.
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07.20.Fw Calorimeters
07.85.-m X- and γ-ray instruments
85.25.Oj Superconducting optical, X-ray, and γ-ray detectors (SIS, NIS, transition edge)

Controlled multipulse loading with a stuffed striker in classical split Hopkinson pressure bar testing

K. Xia, R. Chen, S. Huang, and S. N. Luo

Rev. Sci. Instrum. 79, 053906 (2008); http://dx.doi.org/10.1063/1.2928810 (5 pages)

Online Publication Date: 20 May 2008

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Controlled multipulse loading in classical split Hopkinson pressure bar (SHPB) testing is highly desirable for investigating loading history dependent phenomena but rarely explored. Here, we present a novel technique to achieve controlled multipulse loading in SHPB testing with a stuffed striker. This stuffed striker consists of a striker tube, and a striker bar and a gap enclosed inside the tube; upon impact on the input bar, it can produce two separated loading pulses. The gap controls the delay of the second pulse with respect to the first pulse, and the pulse separation (dwell time) can be continuously tuned from zero to hundreds of microseconds. The combination of the stuffed striker and the Lindholm technique [ J. Mech. Phys. Solids 12, 317 (1964) ] allows for controlled multipulse loading with triple or more pulses. We have validated the working principle of this technique with experiments, and demonstrated its feasibility and flexibility for acquiring relevant dynamic data with double- and triple-pulse loading on polycrystalline Cu. This precisely controlled multipulse loading technique is readily implementable and can be applied to investigating the dynamic response of a wide range of materials.
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07.10.-h Mechanical instruments and equipment
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.F- Deformation and plasticity
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