RSI Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Jul 2008

Volume 79, Issue 7, Articles (07xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 79, 071101 (2008); http://dx.doi.org/10.1063/1.2957649 (11 pages)

S. O. Reza Moheimani

Two-sensor-based feedback control structure for fast and accurate operation of a piezoelectric tube scanner.

Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds

A 1 MA, variable risetime pulse generator for high energy density plasma research

J. B. Greenly, J. D. Douglas, D. A. Hammer, B. R. Kusse, S. C. Glidden, and H. D. Sanders

Rev. Sci. Instrum. 79, 073501 (2008); http://dx.doi.org/10.1063/1.2949819 (5 pages) | Cited 28 times

Online Publication Date: 1 July 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
COBRA is a 0.5 Ω pulse generator driving loads of order 10 nH inductance to >1 MA current. The design is based on independently timed, laser-triggered switching of four water pulse-forming lines whose outputs are added in parallel to drive the load current pulse. The detailed design and operation of the switching to give a wide variety of current pulse shapes and rise times from 95 to 230 ns is described. The design and operation of a simple inductive load voltage monitor are described which allows good accounting of load impedance and energy dissipation. A method of eliminating gas bubbles on the underside of nearly horizontal insulator surfaces in water was required for reliable operation of COBRA; a novel and effective solution to this problem is described.
Show PACS
84.30.Jc Power electronics; power supply circuits
84.30.Ng Oscillators, pulse generators, and function generators
84.30.Sk Pulse and digital circuits
52.59.Qy Wire array Z-pinches
52.50.Lp Plasma production and heating by shock waves and compression

On the reliability of scrape-off layer ion temperature measurements by retarding field analyzers

M. Kočan, J. P. Gunn, M. Komm, J.-Y. Pascal, E. Gauthier, and G. Bonhomme

Rev. Sci. Instrum. 79, 073502 (2008); http://dx.doi.org/10.1063/1.2955465 (10 pages) | Cited 21 times

Online Publication Date: 15 July 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The retarding field analyzer (RFA) is one of the only widely accepted diagnostics for measurements of ion temperature Ti in the tokamak scrape-off layer. In this paper we analyze some instrumental effects of the RFA and their influence on Ti measurements. It is shown that selective ion transmission through the RFA slit is responsible for an overestimation of Ti by less than 14%, even for a relatively thick slit plate. Therefore, thicker slit plates are preferable, since they reduce, e.g., the risk of melting during off-normal events, and the effect of positive space charge inside the cavity. The influence of the electron repelling grid, as well as misalignment of the slit with respect to the magnetic field on Ti measurements are negligible.
Show PACS
52.55.Fa Tokamaks, spherical tokamaks
52.70.-m Plasma diagnostic techniques and instrumentation

Digital smoothing of the Langmuir probe I-V characteristic

F. Magnus and J. T. Gudmundsson

Rev. Sci. Instrum. 79, 073503 (2008); http://dx.doi.org/10.1063/1.2956970 (8 pages) | Cited 11 times

Online Publication Date: 15 July 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Electrostatic probes or Langmuir probes are the most common diagnostic tools in plasma discharges. The second derivative of the Langmuir probe I-V characteristic is proportional to the electron energy distribution function. Determining the second derivative accurately requires some method of noise suppression. We compare the Savitzky–Golay filter, the Gaussian filter, and polynomial fitting to the Blackman filter for digitally smoothing simulated and measured I-V characteristics. We find that the Blackman filter achieves the most smoothing with minimal distortion for noisy data.
Show PACS
52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties
52.80.-s Electric discharges
84.30.Vn Filters
84.30.Sk Pulse and digital circuits

Pulse compression radar reflectometry to measure electron density in plasma with parasitic reflections

Bin Li, Hong Li, Zhipeng Chen, Chen Luo, Huihui Wang, Song Geng, Lei Feng, Qiuyan Liu, and Wandong Liu

Rev. Sci. Instrum. 79, 073504 (2008); http://dx.doi.org/10.1063/1.2947734 (5 pages)

Online Publication Date: 29 July 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Pulse compression radar reflectometry is used to obtain electron density profile in plasma with parasitic reflections in this article. The pulse compression radar relies on the relation between the temporal width of a pulse and the frequency bandwidth of this pulse: Δt∝1/Δf. So a set of sweep-frequency microwaves within a bandwidth Δf can be introduced sequentially into the plasma to obtain the same information as the one obtained by a real pulse. By applying a Fourier transform to the data of reflectivity array in the frequency domain, the temporal response in the time domain is obtained. The limitation of the parasitic reflections on measurement can be eliminated from the temporal response by the method of time gate. This is a prominent advantage when this method is compared to the traditional reflectometry. For this method, an appropriate compromise between the spatial resolution and the electron density resolution is important. Experimental results show that the profile obtained from pulse compression radar reflectometry is similar to that from a double Langmuir probe.
Show PACS
52.70.Gw Radio-frequency and microwave measurements
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
52.25.-b Plasma properties
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close