1. Y. Kisselev PST05 conference 14-17 Nov 05 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. Y. Kisselev PST05 conference 14-17 Nov 05 2 Microwave cavity for the new COMPASS magnet Dynamic nuclear polarization under multimode microwave excitation 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 Frequency modulation effect 1) 3) 4) 5) 2)

3. Y. Kisselev PST05 conference 14-17 Nov 05 3 1.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. The main idea of the presentation: 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. COMPASS, V= 424 cm 3 (2004 y) Time (hour) D -Polarization (%) Irradiated LiD 2.5 Tesla Bouffard *, V= 0.0125 cm 3 (1980 y)

4. Y. Kisselev PST05 conference 14-17 Nov 05 4 Spectrum of frequency modulated microwave signal Frequency bandwidth of FM spectrum equals to 2·Δω max /2π  10 MHz in our exampleif MHz – Frequency deviation Hz – Modulation frequency is the modulation index is the modulation index J i (m) – are Bessel functions m = 1000 Frequency 70 GHz +MHz Intensity Arb. Un.

5. Y. Kisselev PST05 conference 14-17 Nov 05 5 The number of excited modes decreases with decreasing cavity diameter Electric modes Magnetic modes Theory for cylindrical cavity Frequency 70 GHz + MHz ± Number of modes  =23 cm,  82 modes, 34 nondegenerate  F  100 MHz/34  3 MHz  =15 cm,  61 modes, 34 nondegenerate  F  100 MHz/34  3 MHz

6. Y. Kisselev PST05 conference 14-17 Nov 05 6 Microwave sensor for the spectral measurements The device has linear characteristic within 0.÷ 50 microwatt region

7. Y. Kisselev PST05 conference 14-17 Nov 05 7 General view of the new microwave cavity Microwave sensor with preamplifier Display

8. Y. Kisselev PST05 conference 14-17 Nov 05 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. Y. Kisselev PST05 conference 14-17 Nov 05 9 cylindrical cavity 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 Intensity Arb. Un.  F  10 MHz Spectrum of FM-generator Frequency 70 GHz + MHz  =23 cm,  36 modes;  F  100 MHz/36  3 MHz

10. Y. Kisselev PST05 conference 14-17 Nov 05 10 reflector Microwave transmission measuring set-up for multimode load. It enables the tests of the reflected power over the frequency band

11. Y. Kisselev PST05 conference 14-17 Nov 05 11 Finding the shape of coupling holes for the best matching between feeding waveguide and a cavity 70200 MHz 70240 70260 70290 70310 d - matched 8 mm load Matching over the entire band

12. Y. Kisselev PST05 conference 14-17 Nov 05 12 The latest version of the three-cells cavity design. RESUME NEW COMPASS CAVITY for OD-MAGNET Beam line Cavity 1Cavity 2Cavity 3 Heat exchanger Target cell 1 Target cell 2Target cell 3 2.5 K- thermal screen Microwave power

13. Y. Kisselev PST05 conference 14-17 Nov 05 13 Thank You !!!