Y. Kisselev PST05 conference 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:

Y. Kisselev PST05 conference 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)

Y. Kisselev PST05 conference Nov 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) COMPASS, V= 424 cm 3 (2004 y) Time (hour) D -Polarization (%) Irradiated LiD 2.5 Tesla Bouffard *, V= cm 3 (1980 y)

Y. Kisselev PST05 conference 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.

Y. Kisselev PST05 conference 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

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

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

Y. Kisselev PST05 conference 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

Y. Kisselev PST05 conference 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

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

Y. Kisselev PST05 conference Nov Finding the shape of coupling holes for the best matching between feeding waveguide and a cavity MHz d - matched 8 mm load Matching over the entire band

Y. Kisselev PST05 conference Nov 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 K- thermal screen Microwave power

Y. Kisselev PST05 conference Nov Thank You !!!