JINR activity on the Design of the 4th generation Cryomodule. High Precision Laser Metrology. Presented by G. Shirkov* and A. Sukhanova** * JINR/ILC-Project Head ** J. Budagov JINR Dubna group

History -In 2005 the International Committee for Future Accelerators (ICFA) made up a decision to develop an electron–positron linear collider (ILC). -In 2006 the JINR (Dubna, Russia)–VNIIEF (Sarov, Russia)–INFN (Pisa, Italy)–FNAL (Batavia, USA) established a collaboration by the initiative of the JINR and started their activities on the ILC. -In 2007 the JINR officially joined the ILC Project and proposed the Dubna region for the ILC location.

The main participants JINR: N. Azaryan, Yu. Budagov, V. Glagolev, D. Demin, M. Lyablin, B. Sabirov, G. Shirkov, A. Sukhanova, G. Trubnikov; Minsk: A. Akimov, A. Aksenchik, M. Batouritski, S. Demyanov, A. Kuraev, A. Klimza, I. Kizhlay, V. Kniga, S. Kolosov, V. Kopusov, T. Petrochenko, I. Pobol, T. Popkova, A. Rak, N. Shumeiko, A. Sinitsin, R. Stefanovich, A. Zhuravski; Sarov: I. Malkov, V. Perevozchikov, V. Rybakov, V. Zhigalov; INFN Pisa: A. Basti, F. Bedeschi, G. Bellettini, F. Frasconi, S. Linari, A. Ragonesi ; FNAL: E. Harms, B. Kephart, A. Klebaner, D. Mitchell, S. Nagaitsev, L. Ristori, R. Roser, B. Soyars, V. Yarba.

R&D on Ti-SS & Nb-SS Bimetallic transitions JINR principal investigator – B. Sabirov * * J. Budagov group

Specialists from the JINR and VNIIEF (Sarov) have studied an opportunity to manufacture a tube of bimetal type (stainless steel and titanium) by explosion welding. The tube is used as a transitional load-bearing element in the 4th generation cryomodule construction for the ILC. 24 Ti + SS samples were made by using the explosion welding method and tested under extreme conditions: - thermal cycling at the liquid nitrogen temperature (77 K); - tests in vacuum and at the pressure of 6 atm; - exposure to ultrasound; - macroanalysis, microanalysis, and the shear test. The results of the leak tests are as follows: - temperature 300 K– 7.5∙10 −10 Torr ∙ l /s; - temperature 77 К– 7.5∙10 −9 Torr ∙ l /s; - pressure 6.5 atm– <5∙10 −10 Torr ∙ l /s.

2010 is marked by an outstanding achievement - the niobium tube was connected to the stainless steel flange by the explosion welding in Sarov. First 4 samples of Nb-SS transitions were manufactured and tested for : Future Plans are to carry out: - tests after high temperature loading; - manufacturing and test more samples for more statistics; - adjust the Nb-SS units to the real cryomodule shop-drawings. - micro and macro structure analysis; - mechanical strength tests of connections; - vacuum tightness after liquid nitrogen temperature cycling in Torr vacuum and 6 bar pressure; - leak tests at 1.8 K and ultrasonic radiation. The key result: the leak was not detected at the sensitivity level of Torr·l/s.

New Design of The Cavity Connection JINR principal investigator – A. Sukhanova* * J. Budagov group

- the non-accelerating length of the beam pipe could be shortened by a few cm per cavity (about 5%) - the assembling procedure could be sufficiently simplified and the assembling time could be reduced by about an order of magnitude A new design of the connection of the Nb cavity end flanges with the beam pipe has been proposed as a result of experimental testing, ANSYS simulations and cooperation with industrial firms producing special sealing and clamps. The main advantages of this new design: Flanges have been successfully tested at the INFN/Pisa cryogenic laboratory. Future Plans: To continue the current studies by using the higher statistics.

Numerical simulation of the behaviour of the commercially produced Ultra- Flex seal has already been carried out using the ANSYS code for Finite Element Analysis. We determined the optimal geometrical parameters of the seal decreasing residual deformation. Tore diameter mm, tore thickness mm As a result of our analysis we determined the optimal parameters of the Ultra- flex gasket to be manufactured by industry: 8 mm in the tore diameter and 0.65 mm thick. The achievable gasket elastic recovery was increased by a factor of 4 and reached 0.2 mm. For the first time the mathematical motivation was used to compare the Ultra-flex gasket and Helicoflex gasket. The Ultra-flex gasket turned out to be better than the Helicoflex gasket.

High Precision Laser Metrology JINR principal investigator – M. Lyablin* * J. Budagov group

The main task of this R&D is to obtain an extended stable laser beam to be used as a coordinate line for the high precision large distance metrology. Earlier we detected a new phenomenon – laser ray space location stabilization inside a tube with atmospheric air. The detailed studies of the observed effect demonstrated its increase by the order of magnitude, when the ends of the tube are covered with optical windows. This observation indicates a possibility to stabilize the optical parameters of air by standing acoustic wave. The sound produced by the standing wave is haired directly. To confirm this new idea, we executed a direct measurement which gave positive results. The left Figure demonstrates a standing acoustic wave and the right one shows observations of the stable standing wave (Fourier analysis) with the main mode frequency of about 2.5 Hz.

We continued our measurements and obtained direct data on the laser ray position stabilization in the closed tube. The left Figure shows a σ(rms) in the beam location and the right figure – the decrease of σ(rms) as an effect of the tube presence. This figure demonstrates a unique laser beam space uncertainty σ T (L) reached when the beam was passing inside the tube with the ends covered by glass windows This figure shows an impressive gain R=σ B (L)/σ T (L) in beam position precision σ T (L) in comparison to the σ B (L) for the case without the tube

Now we suggest that the laser ray should be used as an extended fiducial line for high precision alignment of the detectors (cryomodules) at very large distances. This idea is based on the effects (we found) of laser ray scattering decrease inside the tube containing the standing acoustic wave. The rights and methods of this discovery are protected by the Russian Federation State Patent № Oct. Sissakian, A., Budagov, Yu., Lyablin, M., Batusov, V. «Laser beam formation device»Sissakian, A. Budagov, Yu.Lyablin, M.Batusov, V.

Future Plans include the following: To investigate the physics origin of possible interference of a laser ray with the acoustic waves in the tube - further study of the effects we have detected, is foreseen. To be specific: - laser beam space spread after passing in the vacuum tube 9 m long; - laser beam propagation inside a tube without standing waves; - laser beam propagation inside a tube with resonance excitation of the standing acoustic wave. The planned experiments should answer the question of a degree of the standing wave influence on the laser ray stability after the beams passing through the tube.

TESLA-Type Cavity JINR principal investigators – N. Azaryan* & D. Demin* * J. Budagov group

In 2010 the JINR, BSU, FNAL, INFN collaboration started the experimental study aimed at obtaining a superconducting Nb-cavity in the frame of ILC cryomodule R&D work. The electromagnetic calculations for 1.3 GHz single- cell cavity were fulfilled. We used different simulation tools and the results fit each other. Shop-drawings of the cavity and requirements specification for its manufacturing have been issued - cavity profile - electric field on beam axis - electric field on cavity wall - magnetic field on cavity wall

One unit of the composed single-cell cavity was delivered from FNAL to JINR and later it was sent to Belarus colleagues to be used as an “reference unit” in the R&D work. Requirements specification for hydraulic punch-free stamping of the half-cells and its welding on the Belarus equipment have been issued. Measurement techniques of the cavity’s electrodynamics characteristics are investigated. Future Plans: - 9-cell cavity calculations and design; - calibration tests of the FNAL cavity to adjust the BSU experimental methods and equipment; - manufacturing & tests of the single-cells. Matrix Nb Plate Fluid Firing-Pin Requirements specifications on stands for cryogenic & RF tests are prepared.

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