Key technologies of vacuum chamber for future Accelerators --NSRL Vacuum Group

Outline Key technologies of vacuum chamber for future Accelerators Vacuum technology international status Vacuum technology status at NSRL Our future plans

Key technologies of vacuum chamber for future Accelerators ★ Lower SEY materials for inhibition of electron cloud ★ NEG-coated vacuum chambers enable small apertures to enable high magnet gradients. ★ Lower activation temperature films to avoid deformation or oxidation, also for energy conservation ★ Lower ultimate pressure ★ Less space for installation of vacuum pumps ★ Cleaner and more smooth inner surface of vacuum chamber * IPAC14, Challenges in the Design of Diffraction Limited Storage Rings, Robert Hettel

The Advantage of NEG film ★ NEG-coated vacuum chambers enable small apertures to enable high magnet gradients. ★ Lower activation temperature for longer time (e.g. 180°C x 24 hours), more compatible with the use of aluminum chambers, has been also successfully applied. ★ The achievement of very low pressure （ 10~ 11 Torr down to 10~ 13 Torr ）. These features are ideal for very narrow, conductance limited chambers, like Insertion Devices (IDs), which cannot be always efficiently pumped by ordinary means. * IPAC14, Challenges in the Design of Diffraction Limited Storage Rings, Robert Hettel

Status--LHC CERN used 6 km of coated chambers in the straight warm sections of LHC, while Pioneered at CERN, used extensively at Soleil, and adopted for MAX-IV and Sirius MBA lattices*. * IPAC14, Challenges in the Design of Diffraction Limited Storage Rings, Robert Hettel Vertical NEG coating facility. Internal coil diameter is 450 mm. Maximum pipe length 6.5 m.

Status--LHC Amorphous carbon thin films with low initial secondary electron yield (SEY 〜 1.0) have been applied as a mitigation material in the SPS vacuum chambers. * 2011, Amorphous carbon coatings for the mitigation of electron cloud in the CERN Super Proton Synchrotron, C. Yin Vallgren et al. (a) Inspection of the extracted a-C coated MBB after operation in the SPS. (b) SEY measurement on the coated MBB magnet beam pipe before and after operation in the SPS.

Status--MAX IV ★ In order to validate the NEG-coating quality and its deposition method on small aperture vacuum chambers, two 1 m long, 21 mm inside diameter stainless steel tubes were prepared and NEG- coated at MAX IV. * IPAC13, NEG THIN FILM COATING DEVELOPMENT FOR THE MAX IV VACUUM SYSTEM, S. Calatroni etc. The extruded copper tubes to be NEG- coated. Examples of two antechamber coating trials.

Status-- Soleil Soleil project has adopted NEG coatings in all straight vacuum vessels of the storage ring (56% of the total circumference). It represents the largest application of NEG coating in synchrotrons so far. * IPAC14, Challenges in the Design of Diffraction Limited Storage Rings, Robert Hettel Soleil chamber with lateral pumping ports. Large coil coating facility.

Status—ESRF ESRF has now 27 NEG coated chambers installed and has upgrading plans to add more. * PAC06, STATUS REPORT ON THE PERFORMANCE OF NEG-COATED CHAMBERS AT THE ESRF, M. Hahn et al. Straight section occupancy as of June 2006.

Status—GSI* GSI use NEG in substantial amount in the FAIR project. To upgrade the vacuum system of the SIS 18, it was coated the internal surface of the quadrupole and dipole chambers with a non-evaporable getter (NEG) thin film. * Thin film getter coatings for the GSI heavy-ion synchrotron upgrade, M.C. Bellachioma et al., Vacuum 82 (2008) 435 – 439 Picture of the magnetron sputtering facility built at GSI used to carry out the NEG coating of the dipole chambers for the heavy-ion synchrotron.

Status--CERL For lack of enough space for lumped pumps, the beam ducts in the vicinity of the SC cavities are NEG-coated. Ultrahigh and dust-free vacuum is required in the vicinity of the superconducting cavities to maintain highly stable CW operation, and these beam ducts are coated with Non-Evaporable Getter (NEG) film. * IPAC13, DESIGN OF THE CERL VACUUM SYSTEM, Y. Tanimoto etc. NEG-coated tube installed inside a series of quadrupole magnets near the injector SC cavity. The tube is wrapped with film heaters for activation.

Status—RHIC etc. Installation of 430m of NEG coated pipes in the warm straight sections of RHIC has proved beneficial to reduce pressure instabilities and to remarkably increase machine luminosity. More NEG coated pipes have be installed at RHIC. Several others facilities like ELETTRA, SLS and Diamond have NEG coated chambers already installed or being installed. * IPAC14, Challenges in the Design of Diffraction Limited Storage Rings, Robert Hettel Vertical coating facility. Various cylindrical pipes (5.5m long) are here coated simultaneously. The magnetic coil is visible at the bottom.

Status--KEKB More than 850 beam pipes have been TiN- coated with the facility in KEK site. Output: 10 ~15 beam pipes per week. Goal is about 1000 beam pipes* Ceramic vacuum chamber with RF shielding & TiN coating** * IPAC14, Construction Status of SuperKEKB, Norihito Ohuchi, Kazunori Akai, Haruyo Koiso, ** IPAC14, The Very High Intensity Future, Jie Wei. IPAC12, PROGRESS IN SUPER B-FACTORIES, K. Akai. TiN coating facility for large- scale production in KEK Tsukuba site.

Vacuum technology status at NSRL 1 ， TiN coated stainless steal pipes ( 10 years ago) ★ TiN coated undulator vacuum chamber at Hefei light with a size of Ф 86 mm x 3000 mm ★ Also, film coating on 5 meters long pipes’ inner faces are OK for us. ★ Straight and curved pipes are OK for us. Current running situation ★ TiZrV coated undulator pipes had been installed in Hefei light source storage ring.

Vacuum technology status at NSRL 2 ， TiZrV/Pd NEG film ※ Advantage ★ The H 2 sorption capacity of the NEG- Pd film is higher compared with TiZrV film. ★ The number of possible regenerations is, in principle, endless. ★ the lifetime of the film is strongly enhanced. * C. Paolini, M. Mura, and F. Ravelli, Efficient combining of ion pumps and getter-palladium thin films, Journal of Vacuum Science & Technology A 26, 1037 (2008)

Vacuum technology status at NSRL 2 ， TiZrV/Pd NEG film Hydrogen pumping- speed curves for pumps A and B, plotted as a function of pressure. The behavior of the NEG-Pd-coated pumps is compared to that of identical pumps, subjected to the same thermal cycle, but without the film. * C. Paolini, M. Mura, and F. Ravelli, Efficient combining of ion pumps and getter-palladium thin films, Journal of Vacuum Science & Technology A 26, 1037 (2008) Typical pressure descent at the end of the baking- activation cycle for a NEG-Pd- coated pump.

Vacuum technology status at NSRL 2 ， TiZrV/Pd NEG film ★ TiZrV/Pd film coated pipe with a size of 86 mm in diameter and 1000 mm in length. （ a ） # TiZrV （ b ） # Pd （ c ） # TiZrV /Pd Fig. Cross section morphology images (left) and surface topography images (right) of of TiZrV film deposited on silicon by scanning electron microscop (a), nm of Pd film deposited on silicon (b), and a 480 nm of Pd film deposited on deposited on of TiZrV film. The film coating parameters were the same for Pd film in (b) and (c). TiZrV/Pd NEG film coating equipment at NSRL.

Vacuum technology status at NSRL 3 ， TiN coated ceramic pipes ※ Advantage ★ low secondary electron yield (SEY) ★ good electrical conductivity ★ stability of performance ★ ability to block hydrogen permeation TiN film coating equipment for ceramic pipes at NSRL.

Vacuum technology status at NSRL 4 ， SEY tests--TiZrV film SEY of TiZrV film as received and after 2 hours heating at 200 ℃ as a function of incidence electron energy at NSRL. SEY of TiZrV/SS at SLAC. Top figure: as received (dotted line), activated at 210 ℃, 2 h (dashed line, lower SEY max) and vacuum recontaminated after 134 days at normal incidence and 145 days at 23°incidence (solid line). Bottom figure: electron conditioning (solid line) vacuum recontaminated after 34 days (dashed line) and re-activated, 210 ℃, 2h (dotted line).

Vacuum technology status at NSRL 4 ， SEY tests—TiN film SEY of five TiN/SS samples, as received, measured at 23° primary incidence at SLAC.

Vacuum technology status at NSRL 4 ， SEY tests— Stainless steal and OFHC Cornell University NSRL

Our future plans 1, Higher precision SEY testing device ★ New SEY testing device is under the assembly process. Goals (i) measuring the SEY of different material surfaces that are used for beam chambers; (ii) the effect of temperature, incidentangle, cleanliness, current intensity on the SEY of different materails; (iii) comparing different materials and mitigation coatings. Higher precision SEY testing device at NSRL.

Our future plans 2, Develop new low SEY materials≤1.2 ★ Different coatings on the stainless steel base will be studied to reduce the wall impedance and secondary electron yield at 4-60 K. ★ The possibility of further improvement by substituting palladium with other Pd-based alloys will also be evaluated. ★ Amorphous carbon coatings preparation technology.

Our future plans 3, New high hydrogen pumping speed material ★ During the study for developing of the TiZrV getter alloy, it was proposed that it may be advantageous to replace the palladium overlayer with PdAg alloys, which provide an easier transmission of H 2 to the underlying NEG. ★ Lower cost ★ Further investigation in this direction is needed.

Our future plans 4, Lower activated-temperature film ★ Wider application range ★ energy conservation ★ Further investigation in this direction is needed. 5, Establish a film coating equipment for small apertures vacuum chambers

--NSRL Vacuum Group