No abstract

The pumps selected for storage ring vacuum systems must efficiently pump helium and hydrogen at pressures below 10−10 Torr. In addition, they have to work in a background of nuclear radiation. The presence of an ample supply of liquid helium in the proposed Intersecting Storage Accelerator (ISABELLE) makes cryosorption pumping very attractive. We have investigated, therefore, the behavior of Linde Type 5A molecular sieve, bonded to a stainless steel panel, at 4.2 and 5 K in the pressure range from 10−11 to 10−8 Torr. By fitting our experimental data, we obtained the constants K and B in the equation ϑ = K exp(−ε2B) which can be used to calculate the adsorption isotherms for helium and hydrogen on bonded molecular sieve 5A at various temperatures. Furthermore, we have determined the causes of a steeper slope of the isotherms in the 10−11 Torr range. Finally, a pump containing a cryosorption panel was exposed to a flux of 1.7×105 protons and pions per second which resulted in no pressure change. Based on the reults of this investigation, we have designed a cryosorption pump which can be operated at 4.2 K either inside or outside the superconducting magnet dewars.

The presence of an ample supply of liquid helium in the proposed Intersecting Storage Accelerator (ISABELLE) makes cryosorption pumping very attractive for maintaining a long vacuum chamber below 10-10 Torr. We have investigated, therefore, the behaviour of Linde Type 5 A molecular sieve, bonded to stainless steel panel, at 4.2 and 5 K in the pressure range from 10-11–10-8 Torr. By fitting our experimental data we obtained the constant B for helium and hydrogen in the Dubinin-Radushkevich equation which is used to calculate adsorption isotherms at various temperatures. In particular, we studied the causes of a steeper slope of the isotherms in 10-11 Torr range. Based on the results of this investigation we have designed a cryosorption pump to be operated at 4.8 K inside the superconducting magnet dewars in ISABELLE. The pump contains 120 cm2 of bonded molecular sieve and can adsorb more than 1000 cm3 (STP) of helium while maintaining the pressure below 1×10-10 Torr. Its pumping speed is limited only by the conductance of chevrons.

The superconducting sagnets for ISA3ELLE-Jill use a forced flow supercritical helium cooling system. In order :a evaluate this cool ins scheme cwo Individual dipole magnets ware first tested in conventional dewars using pool soiling heliua. These sagnecs were then modified for forced flow cooling and receescd wich che idencictl signae coils. Ine fir« (valuation cesc used lU long ISA model dipole magnet whose pool builing performance had been esubllshcd. 5>.e sasa magnet, was cheo reeested with forced flow cooling, energising ic at various operacing temperatures until quench occurred. The magnet's performance wish forced flow cooling was consistent with data from the previous pool boiling casts. The next step in the program was a fall-scale ISA3ELLE dipote ring nagnat, 4.25 a long, whose perfaroance was first evaluated with pool boiling. For che forced flow test she nagnec was shrunk-fit into an unsplic laainatad core encased in a stainless steel cylinder. The high pressure gas is cooled below 4 X by a helium bath which is pumped below atmospheric pressure with an ejector nozzle. The performance of the full-scale dipole magnet in the new configuration with farced flow cooling, showed a 102 increase in the atcainable maximm currsne as compared Co she pool boiling data.

The study of S-Band superconducting niobium cavities is being carried out for application to long-pulse rf beam separators in the momentum range of the AGS, whereas, X-Band frequencies are being considered for the HAL accelerator. Results for a S-cell S-band prototype are: a peak field of 410 G, corresponding to an equivalent deflecting field of over 2 MV/tn, and a loss Improvement factor of 2 x Ifl5. The fabrication and post-fabrication treatments are described. Perturbation measurements to determine deflector parameters are summarized. A new type of node stabilizer is suggested. A 7-cell X-Band deflector is under construction. IntroductionThe study of rf superconductivity has the potential application to rf separators for counter experiments which require the separator to be operational , for several hundred milliseconds.1 Estimates of particle fluxes for the Multi-Particle Spectrometer facility now under construction 2 indicate that long-pulse superconducting separators would be desirable, but : lack of funds postponed the actual construction of a . separated beam. ,The design of the BNL separator*-"* assumed three 2.5-m long deflecting cavities operating at 2.855 GHz (S-Band) and capable of an equivalent defelection of initially E o = 2 MV/m and later on 4 MV/to. A 5-cell test cavity was designed and fabricated. This BNL test cavity closely resembles the Karlsruhe cavity S IV.-*"' Long-pulse rf separators are also of interest to NAL. To obtain a realistic basis for a design, we have fabricated an 8-cell test deflector operating at 8.66 GHz (X-Band). Results are forthcoming.