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Oct 2009

Volume 80, Issue 10, Articles (10xxxx)

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Rev. Sci. Instrum. 80, 101101 (2009); http://dx.doi.org/10.1063/1.3236681 (22 pages)

David D. Nolte

Biodisks are lab-on-a-chip device that spin. The two major types of biodisks are centrifugal microfluidic disks and BioCDs. The microfluidic disks use noninertial forces to pump and switch fluids. The BioCDs use lasers and high-frequency optical sampling to rapidly measure target analytes bound to recognition molecules.

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Design and characterization of supersonic nozzles for wide focus laser-plasma interactions

N. Lemos, N. Lopes, J. M. Dias, and F. Viola

Rev. Sci. Instrum. 80, 103301 (2009); http://dx.doi.org/10.1063/1.3233895 (5 pages) | Cited 2 times

Online Publication Date: 5 October 2009

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In this work we optimize the contour of supersonic nozzles to produce long and stable gas jets suitable to be used in loose focus laser-plasma applications. The nozzle design method takes into account the inclusion of a boundary layer that increases the length of the usable gas jet. Two 8 mm supersonic nozzles were characterized, one with a Mach number of 3 and another with a Mach number of 6, using a Mach–Zehnder interferometer performed with a He:Ne 4 cm expanded laser beam. The experimental results confirm that the inclusion of the boundary layer produces an 8 mm constant longitudinal density profile for the nozzle with a Mach number of 6 (NM6) and a 4.5 mm constant longitudinal density profile for the nozzle with a Mach number of 3 (NM3).
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52.30.-q Plasma dynamics and flow
52.40.Hf Plasma-material interactions; boundary layer effects
52.75.-d Plasma devices

Complementary ion and extreme ultra-violet spectrometer for laser-plasma diagnosis

S. Ter-Avetisyan, B. Ramakrishna, D. Doria, G. Sarri, M. Zepf, M. Borghesi, L. Ehrentraut, H. Stiel, S. Steinke, G. Priebe, M. Schnürer, P. V. Nickles, and W. Sandner

Rev. Sci. Instrum. 80, 103302 (2009); http://dx.doi.org/10.1063/1.3239403 (5 pages) | Cited 3 times

Online Publication Date: 21 October 2009

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Simultaneous detection of extreme ultra-violet (XUV) and ion emission along the same line of sight provides comprehensive insight into the evolution of plasmas. This type of combined spectroscopy is applied to diagnose laser interaction with a spray target. The use of a micro-channel-plate detector assures reliable detection of both XUV and ion signals in a single laser shot. The qualitative analysis of the ion emission and XUV spectra allows to gain detailed information about the plasma conditions, and a correlation between the energetic proton emission and the XUV plasma emission can be suggested. The measured XUV emission spectrum from water spray shows efficient deceleration of laser accelerated electrons with energies up to keV in the initially cold background plasma and the collisional heating of the plasma.
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52.70.-m Plasma diagnostic techniques and instrumentation
07.60.Rd Visible and ultraviolet spectrometers
42.79.Ls Scanners, image intensifiers, and image converters
52.20.-j Elementary processes in plasmas
52.38.-r Laser-plasma interactions

Modal response of 4-rod type radio frequency quadrupole linac

Avik Chatterjee, Abhijit Mahapatra, Manas Mondal, and Alok Chakrabarti

Rev. Sci. Instrum. 80, 103303 (2009); http://dx.doi.org/10.1063/1.3247904 (7 pages)

Online Publication Date: 21 October 2009

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This paper deals with the analysis and experimental study of natural frequencies of vibration of a 4-rod type radio frequency quadrupole (RFQ) linear accelerator. The eigenvalue analysis of the structure has been done both analytically (multispan beam concept) as well as using blocked Lanczos eigenvalue finite element solver with an ability to extract the rigid body modes. This has been done in the mechanical design phase to find the level of agreement between the output of simplified analytical analysis results and the output of a commercial finite element method (FEM) solver, since a full scale RFQ structure is too complex to handle analytically. Experimental validation of the analysis results has been done on the physical 1.7 m RFQ at the installation site. The experimental data obtained were later analyzed and found to be in close agreement with the predicted frequencies in the lower frequency ranges. It gets more and more deviated in the higher frequency ranges. Also some frequencies were observed during experimentation, which were not found in the finite element analysis results. The source of those frequencies are to be further investigated as it may play a predominant role in the design high quality factor beam line cavities for higher operational efficiency.
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29.20.Ej Linear accelerators
29.27.Bd Beam dynamics; collective effects and instabilities
29.27.Eg Beam handling; beam transport

Calorimetric low temperature detectors for low-energetic heavy ions and their application in accelerator mass spectrometry

S. Kraft-Bermuth, V. A. Andrianov, A. Bleile, A. Echler, P. Egelhof, A. Kiseleva, O. Kiselev, H. J. Meier, J. P. Meier, A. Shrivastava, M. Weber, R. Golser, W. Kutschera, A. Priller, P. Steier, et al.

Rev. Sci. Instrum. 80, 103304 (2009); http://dx.doi.org/10.1063/1.3213622 (9 pages)

Online Publication Date: 26 October 2009

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The energy-sensitive detection of heavy ions with calorimetric low temperature detectors was investigated in the energy range of E = 0.1–1 MeV/amu, commonly used for accelerator mass spectrometry (AMS). The detectors used consist of sapphire absorbers and superconducting aluminum transition edge thermometers operated at T ∼ 1.5 K. They were irradiated with various ion beams (13C,197Au,238U) provided by the VERA tandem accelerator in Vienna, Austria. The relative energy resolution obtained was ΔE/E = (5–9)×10−3, even for the heaviest ions such as 238U. In addition, no evidence for a pulse height defect was observed. This performance allowed for the first time to apply a calorimetric low temperature detector in an AMS experiment. The aim was to precisely determine the isotope ratio of 236U/238U for several samples of natural uranium, 236U being known as a sensitive monitor for neutron fluxes. Replacing a conventionally used detection system at VERA by the calorimetric detector enabled to substantially reduce background from neighboring isotopes and to increase the detection efficiency. Due to the high sensitivity achieved, a value of 236U/238U = 6.1×10−12 could be obtained, representing the smallest 236U/238U ratio measured at the time. In addition, we contributed to establishing an improved material standard of 236U/238U, which can be used as a reference for future AMS measurements.
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07.75.+h Mass spectrometers
29.40.-n Radiation detectors
07.20.Dt Thermometers
07.20.Fw Calorimeters
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