• Yu.Belchenko, A.Burdakov, V.Davydenko, V.Dolgushin, A.Dranichnikov, A.Ivanov, A.Khilchenko, V.Kobets, S.Konstantinov, A.Krivenko, A.Kudryavtsev, M.Tiunov, V.Savkin, V.Shirokov, I.Sorokin,
  Budker Institute of Nuclear Physics, Novosibirsk, Russia

• J.P.Farrell
  Brookhaven Technology Group, Inc., USA

Status of original 2.0 MeV, 10 mA proton tandem-accelerator with vacuum insulation is presented. The accelerator is intended to be used in facilities generating resonance gamma rays for explosives detection and epithermal neutrons for boron neutron-capture therapy of brain tumors. Steady-state sectioned rectifier from industrial ELV-type electron accelerator is used as a high voltage source for the accelerator. A dc high-current negative ion source has been developed for injection into the tandem. In the tandem accelerator there is set of nested potential electrodes with openings which form a channel for accelerated negative ion beam and subsequently for proton beam after stripping gas target. The electrodes are fixed on a high voltage feedthrough insulator though which required potentials are applied to them from the rectifier by means of resistor voltage divider. In the paper the first experimental results obtained with vacuum insulated tandem accelerator are also given. Keywords: vacuum insulation tandem accelerator, gamma resonance absorption, boron neutron capture therapy.

135

MOHP02

• V.V.Anashin, A.N.Dranichnikov, R.V.Dostovalov, A.V.Evstigneev, L.G.Isaeva, A.A.Krasnov, V.S.Kuzminykh, L.M.Schegolev, Yu.M.Shatunov
  Budker Institute of Nuclear Physics, Novosibirsk, Russia

Perimeter of VEPP-2000 is 24.4m only and the average density of SR flux is 1.2*10¹⁹ photon/s per meter and SR power is 1000W per meter at maximum design currents Ie-=Ie+=200mA. Special SR receivers are used along the total length of the ring except interaction regions and RF cavity. An intense gas load due to photon stimulated desorption should be compensated by high enough molecular pumping speed. VEPP-2000 high vacuum system consists from different parts: 8 vacuum chambers inside the dipole magnets, vacuum chambers of the solenoids, experimental and technical straight sections and vacuum chamber of the RF cavity. VEPP-2000 high vacuum pump system consists from 16 ports with ion-getter pumps PVIG-100 situated on the bending magnets vacuum chambers edges; ion- getter pump PVIG-250 connected with resonator area; 4 cryopumps presented by solenoid cold surface. To prevent SR heating of cryosurface at T=4.2 K a perforated cooper liner have been made that is cooled by liquid nitrogen. Slits in the liner should provide linear pump speed at rate of 5 l/sec/cm for nitrogen. Cold surface at 4.2 K is the ideal pump for all residual gases except hydrogen, since after adsorption more than one monolayer of hydrogen at T=4.2 K saturated vapor pressure the one reaches 5*10^-7 Torr. In spite of such circumstances calculations showed the beam lifetime will be determined of CO residual pressure. By now the vacuum system has been made, assembled, pumped and baked in-situ at 200С. The obtained average pressure in vacuum chamber of storage ring is better than 10^-9 Torr. But pressure is about 10^-9 Torr inside resonator vacuum chamber baked in-situ at 120C.