Spectrometer, Grating, Rotation
Wednesday, September 20, 2006
A Rotating Grating Spectrometer has been designed and developed, which can be mounted on top of the rotor of a turbo molecular pump with a maximum rotating speed of 43,200 rpm. The pumps rotor is magnetically supported resulting in minimal mechanical vibrations.
The Grating and the pump rotating blades are machined from a solid aluminum block, which is mounted to the top of the shaft. The shaft diameter is 235 mm and the shaft height is 331 mm. The diameter of the Grating is 134 mm and the total number of grooves is 2000 with a blaze angle of 45°. The material of the vacuum window for both the incident and diffracted beams is Teflon or crystal quartz. The window thickness is 3 mm and a 40 mm diameter.
It takes about three minutes for the Spectrometer to reach steady state revolutions. The laser light beam is chopped at the exit of the Laser and the reference light beam is blocked from the photodetector. This configuration provides an output AC voltage of the photodetector, which is nearly proportional to the input light beam power. A comparison is made between the output voltages from the light beam diffracted from the grating in the stationary position, with the voltage due to a light beam reflected from a flat mirror replacing the grating.
Source: , “Frequency shift of 1.45 MHz for 337-m HCN laser beam with a super rotating grating” by T. Maekawa, T. Minami, K. Makino, S. Tanaka, S. Kubo, and M. Iguchi; Rev. Sci. Instrum. 62(2), February 1991; Maekawa, Minami, Makino, Tanaka, Department of Physics, Kyoto University, Kyoto 606, Japan; Kubo, National Institute for Fusion Science, Nagoya 464-01, Japan; Iguchi, Hachiohji Factory, Osaka Vacuum, Ltd., Hachiohji 193, Japan
Reference: None Available
Industrial Products
posted by JD52 @ 8:37 PM,
