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Nov 2009

Volume 80, Issue 11, Articles (11xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 80, 111101 (2009); http://dx.doi.org/10.1063/1.3224703 (17 pages)

R. Vijay, M. H. Devoret, and I. Siddiqi

Poincaré sections of an RF-driven Josephson junction oscillator. Right: Oscillator biased near the upper bifurcation point (IRF=IB+) where two attractors OL and OH coexist. The transition from OL to OH forms the basis of a sensitive threshold amplifier. Left: Oscillator biased outside the bistable region where a single attractor exists.

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Repetitive production of positron emitters using deuterons accelerated by multiterawatt laser pulses

Masatoshi Fujimoto (藤本正俊), Koji Matsukado (松門宏治), Hironori Takahashi (高橋宏典), Yoichi Kawada (河田陽一), Shinji Ohsuka (大須賀慎二), and Shin-Ichiro Aoshima (青島紳一郎)

Rev. Sci. Instrum. 80, 113301 (2009); http://dx.doi.org/10.1063/1.3256113 (5 pages) | Cited 2 times

Online Publication Date: 9 November 2009

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Positron emitters 11C, 13N, and 15O, which can be used in positron emission tomography, were produced using deuterons accelerated by irradiation of laser pulses ∼ 70 TW in peak power and ∼ 30 fs in duration with a repetition of 10 Hz during a period of as long as 200 s. Every laser pulse irradiates the fresh surface of a long strip of a solid-state thin film. Deuterons contained in the film are accelerated in the relativistic plasma induced by the pulse. The deuterons are repetitively incident on solid plates, which are placed near the film, to produce positron emitters by nuclear reactions. The radioactivities of the activated plates are measured after the termination of laser irradiation. In activation of graphite, boron-nitride, and melamine plates, the products had total activities of 64, 46, and 153 Bq, respectively. Contamination in the setup was negligible even after several thousands of laser shots. Our apparatus is expected to greatly contribute to the construction of a compact PET diagnostic system in the future.
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07.77.Ka Charged-particle beam sources and detectors
41.75.Fr Electron and positron beams
87.57.uk Positron emission tomography (PET)
29.25.Bx Electron sources

Direct high-resolution ion beam-profile imaging using a position-sensitive Faraday cup array

Lauri Panitzsch, Michael Stalder, and Robert F. Wimmer-Schweingruber

Rev. Sci. Instrum. 80, 113302 (2009); http://dx.doi.org/10.1063/1.3246787 (6 pages) | Cited 5 times

Online Publication Date: 10 November 2009

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Ion sources have wide-spread use in a multitude of applications. For many, an accurate knowledge, or better, an accurate imaging, of the beam profile and intensity is an important criterion. We are developing an ion source to calibrate instruments for space-based measurements of solar wind and suprathermal particles in the energy range from below 1 keV/nuc to above 200 keV/nuc. In order to establish accurate beam profiles for calibration purposes, we have developed a new method based on an array of very small (∅ = 0.3 mm) Faraday cups. Here, we describe the experimental setup and discuss how to achieve several requirements such as a large thermal load due to the ∼ 40W of beam power.
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29.40.Gx Tracking and position-sensitive detectors
06.20.fb Standards and calibration
07.77.Ka Charged-particle beam sources and detectors
29.25.Ni Ion sources: positive and negative

A short pulse (7 μs FWHM) and high repetition rate (dc-5kHz) cantilever piezovalve for pulsed atomic and molecular beams

Daniel Irimia, Dimitar Dobrikov, Rob Kortekaas, Han Voet, Daan A. van den Ende, Wilhelm A. Groen, and Maurice H. M. Janssen

Rev. Sci. Instrum. 80, 113303 (2009); http://dx.doi.org/10.1063/1.3263912 (6 pages) | Cited 11 times

Online Publication Date: 23 November 2009

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In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 μs have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 μm nozzle releases about 1016 particles/pulse and the beam brightness was estimated to be 4×1022 particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5×10−6 Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow (Δv/v = 2%–3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas load of the cantilever valve makes it possible to design very compact single chamber molecular beam machines with high quality cold and intense supersonic beams. The high speed cantilever piezovalve may find broad applicability in experiments where short and strong gas pulses are needed with only modest pumping, the effective use of (expensive) samples, or the production of cold atomic and molecular beams.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors
29.40.-n Radiation detectors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
29.25.-t Particle sources and targets
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