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PST05 Conference

PST05 Conference. Microwave cavity for large COMPASS polarized target By: Y. Kisselev , J. Ball, G. Baum, N. Doshita, F. Gautheron, J. Heckmann, J. Koivuniemi, K. Kondo, S. Platchkov, A. Magnon, G. Mallot, W. Meyer, G. Reicherz. COMPASS PT- team at CERN Introduces:. 1). 2). 3). 4).

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PST05 Conference

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  1. PST05 Conference Microwave cavity for large COMPASS polarized target By: Y. Kisselev, J. Ball, G. Baum, N. Doshita, F. Gautheron, J. Heckmann, J. Koivuniemi, K. Kondo, S. Platchkov, A. Magnon, G. Mallot, W. Meyer, G. Reicherz COMPASS PT- team at CERN Introduces:

  2. 1) 2) 3) 4) 5) Microwave cavity for the new COMPASS magnet Dynamic nuclear polarization under multimode microwaveexcitation Frequency modulation effect Spectral structure of a large cylindrical cavity Design of the coupling hole between feeding waveguide and the cavity The last release of the three-cells cavity design

  3. COMPASS, V= 424 cm3 (2004 y) D -Polarization (%) Bouffard *, V= 0.0125 cm3 (1980 y) Irradiated LiD 2.5 Tesla Time (hour) The main idea of the presentation: • To provide resonant excitation of a non-tunable cavity of polarized target with high intensity of a cavity microwave field • 2. To provide the best spatial MW-uniformity in the target material • as required for the highest polarization. Solution: use of MW frequency modulated with a bandwidth covering several modes of the cavity Advantage: 1. Shortened DNP- built up time. 2. Deuteron polarization > 50 % *V. Bouffard, Y. Roinel, P. Roubeau and A.Abragam. J. Physique 41 (1980) 1447-1451.

  4. if MHz – Frequency deviation Ji(m) – are Bessel functions Hz – Modulation frequency is the modulation index Intensity Arb. Un. Frequency 70 GHz +MHz Spectrum of frequency modulated microwave signal m = 1000 Frequency bandwidth of FM spectrum equals to 2·Δωmax/2π 10 MHz in our example

  5. Electric modes Magnetic modes • =23 cm,  82 modes, 34 nondegenerate F  100 MHz/34  3 MHz ± Number of modes • =15 cm,  61 modes, 34 nondegenerate F  100 MHz/34  3 MHz Frequency 70 GHz + MHz Theory for cylindrical cavity The number of excited modes decreases with decreasing cavity diameter

  6. Microwave sensor for the spectral measurements The device has linear characteristic within 0.÷ 50 microwatt region

  7. Display Microwave sensor with preamplifier General view of the new microwave cavity

  8. Position of the whip-antenna in the cavity The rigid coaxial cable has a considerable attenuation about 10 dB/m or more. The MW energy induced in the NMR coils can dissipate inside the cable made a parasitic MW-absorption

  9. =23 cm,  36 modes; F  100 MHz/36  3 MHz Intensity Arb. Un. Frequency 70 GHz + MHz F  10 MHz Spectrum of FM-generator The experimental mode spectrum of the cylindrical cavity Cylindrical cavity Important remark:All of the above modes have different intensity therefore the coupling between feeding waveguide and a cavity must be inspected

  10. Microwave transmission measuring set-up for multimode load. It enables the tests of the reflected power over the frequency band reflector

  11. 70200 MHz 70240 70260 70290 70310 matched 8 mm load d - Matching over the entire band Finding the shapeof coupling holes for the best matching between feeding waveguide and a cavity

  12. Microwave power Target cell 2 Target cell 3 Target cell 1 Heat exchanger Beam line Cavity 1 Cavity 2 Cavity 3 2.5 K- thermal screen RESUME The latest version of the three-cells cavity design. NEW COMPASS CAVITY for OD-MAGNET

  13. Thank You !!!

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