Possible Configurations for Prototypes of PX Cryomodules: SSR0 and SSR1 Prepared for discussion at the HINS  PX technical meeting 12/10/20101I. Terechkine

Content Focusing lens specifications for HINS. Guideline for cryomodule work as of summer 2010; Current work on the cryomodule: what and why. What we need to study using a pre-prototype cryomodule. Plans for future work with beam. What is needed and what is optimal Possible ways to proceed with the cryomodule work 12/10/20102I. Terechkine

HINS Lens Specifications RT sectionSS1SS2 Bore diameter20 mm30 mm Squared Field Integral1.8 T 2 -m3.0 T 2 -m5.8 T 2 -m Magnetic Field on Cavity Walls (*)~50 Gs~0.01 Gs (**) Temperature4 K4 K (***) Goal Length (#)235 mm315 mm350 mm Dipole Corrector Strength (##)0.25 T-cm0.5 T-cm no data Alignment precision of ends of the effective length 0.3 mm (with correctors) no data 12/10/2010I. Terechkine3 The table is a product of several iterations in the HINS project history; it was changed several times during the solenoid-based lens R&D. (*) – The nearest wall was assumed when the fringe field was evaluated. (**) – Later it was changed to 0.1 Gs – see TD note TD (***) - 2K option was discussed, but rejected because of the lack of cooling power at 2 K. (#) - It was always confusion about what length is available because no integration work was done. (##) – about a third of all lenses were equipped with corrector dipoles

Cryomodule-Related Work Start design of “short” (3 cavities, 4 solenoids) pre-prototype (I call it concept) CM now. – may not need correctors and BPMs in this CM Demonstrate that the solenoids (beam axis) can be aligned to 0.5 mm rms. By Oct 2011 Install SSR0 prototype CM at MDB no later than Apr Test SSR0 “short” cryomodule (3 cavities, 4 solenoids+correctors, 4 BPMs) with beam and broad-band chopper – Must be a prototype for a “long” cryomodule – Alignment: 0.5 mm rms – By Sept (CD3) Copied from the PX document 608-v1, May 12, 2010: 12/10/20104I. Terechkine Comment: 1. We attempt to use existing elements developed for HINS as the pre-prototype CM design input 2. For only four (4) lenses in the cryomodule, it has little sense to talk in the rms terms. Lets assume we allow maximum deflection of each end of the lens cold mass (not the end points of the effective length, as it was assumed for HINS) from the desired position of 0.5 mm (any direction).

Lattice Period - 1 Initial request is to have 750 mm lattice period in the SSR1 section 12/10/2010I. Terechkine5 SSR1 325 MHz cavities are in production with ~10 totally to fabricate in 2011 SSR1 focusing lens is ready for production. Strand is available for ~10 lenses. Impossible to assemble with the existing parts

Lattice Period - 2 Existing elements can be assembled if the lattice period is 800 mm 12/10/2010I. Terechkine6 BPM is not a part of the SSR1 lens No space for a BPM in the beamline New beamline element(s) must be developed for the SS1

Prototype Cryomodule Design Status 12/10/2010I. Terechkine7 Although preliminary studies were conducted back in 2009, the pre-prototype CM design work started honestly in June 2010

More Views 12/10/2010I. Terechkine8

Plans for the Prototype Cryomodule FRS: PX doc. 794-v1 It is assumed that this prototype cryomodule is built for a two-fold purpose: 1) To address engineering design and component alignment questions pertinent to developing a final 325 MHz spoke cavity cryomodule design for proposed Project X; 2) To test the performance of superconducting spoke type cavities in the presence of and accelerating a low-energy, high-intensity (~2 milliampere) beam. The cryomodule shall incorporate four cells with cavity-to-cavity center spacing of 800 mm. Each solenoid magnet package shall have integral X-Y steering dipoles and an associated X-Y beam position monitor. The cryomodule is being built to understand achievable alignment tolerances. 12/10/2010I. Terechkine9 Guiding idea as of summer 2010: As the design of the concept cryomodule is complete and procurement starts, immediately switch to the SSR0 prototype cryomodule design. SSR0 cavity design, as well as corresponding focusing lens design should be finalized by the time the CM design is finished. This presumes the CM assembly and functionality priority.

It is fine to change plans, but… It is time to refine our understanding of what we expect from the concept cryomodule, and whether we need a separate prototype SSR0 cryomodule. For tests with beam, a test plan and corresponding beam optics must be developed having in mind the arrangement of elements and C-W interfaces in the concept cryostat. Having this work made now can provide valuable feedback to the design team. Based on this work, sound requirements for the concept SSR0 cryomodule can be stated. 12/10/2010I. Terechkine10

What work with the concept cryostat must be done? Test all assembly procedures (not developed yet) Test cryogenic system performance Test performance of RF cavities (that presumably were tested in a test cryostat before being mounted in the concept cryostat) Test focusing system, including power supply, lens training, and protection Test alignment procedures during assembly and verification process when the assembly is in the cryomodule Expect the procured cryovessel in the end of the FY 2012; assembly in the MB is completed in the end of the FY 2013; so we have ~1 year to complete required tests w/o beam. 12/10/2010I. Terechkine11

How to configure the SSR0 prototype cryostat Using the same cryovessel (800 mm period) does not make it a prototype – a system is needed which is close to what is wanted, that is with the desired period of ~650 mm and with BPM-s. Any lens that meets the strength requirement can be used for tests with beam – we have some freedom in choosing the elements for the prototype. Currently, in the prototype SSR0 cryomodule, we can try to use the next lenses: - There are ~20 (12 T1 + 7 T2) available cold masses fabricated and tested for the CH section of HINS linac. totally. We can talk about using these lenses if requirements for the fringe field are relaxed. - SSR1 lenses, although ready for production, still need to go through the production and testing stages. - Other lenses specially designed for this purpose. 12/10/2010I. Terechkine12 The next slides present possible ways of configuring the prototype cryostats (both SS1 and SS0).

Prototype SSR0 PX cryomodule with CH section HINS lenses 1.8 T A ; T = 4 K 12/10/2010I. Terechkine13 Beam pipe is not a part of the lens, so only one bellow is needed. Lens alignment process is fully decoupled

Prototype SSR0 PX cryomodule with CH section HINS lenses - BP monitor 12/10/2010I. Terechkine14 BPM (of any kind) can be inserted inside the lens as a separate unit

Concept SSR1 PX cryomodule with CH-T2 HINS lenses and BPM 12/10/2010I. Terechkine15 Using the HINS CH section lens for the SSR1 cryomodule seems also feasible

Prototype SSR0 PX cryomodule with HINS SSR1 lenses and BP monitor 12/10/2010I. Terechkine16 Cold beam pipe  two bellows are needed and only button type BPM can be used Lattice period of ~700 mm looks achievable

New Design for the SSR0 Section 12/10/2010I. Terechkine17 The lens does not have a soft steel flux clamp. The lens does not have bucking coils The lens does have dipole correctors Strand seems available from Oxford Instruments Design is attractive because it is simple, and provides more space in the beamline Can be further simplified if the fringe field requirements are relaxed.

Fringe Field Map for the SSR0 Lens 12/10/2010I. Terechkine18

Some Summary CH-T2 lens can be used both in the SSR0 and SSR1 cryomodules. Type of a strand used for the CH lens production does not exists any more – new strand will require some modification of the design, although not so big. In the SSR0 prototype cryomodule, the use of CH-type lens will provide big current margin due to lower temperature; for the production cryomodule, a modified design can be used that will help to save more space. In the SSR1 cryomodule, the CH-type lens will work with the stress level that it has been tested for. Nevertheless, some tests will be needed to be sure. New SSR0 lens design require much less strand. Prototyping is needed with 2K test. The CH and SSR0 lenses only can be used in the cryomodules in the case when the fringe field requirement is relaxed. 12/10/2010I. Terechkine19

Technical Issues – Solenoid Focusing The fringe field at the location of the cavity has been reduced to 10 Micro Tesla using bucking coils and shielding. This is an outstanding result considering the space limitations and strong field of the solenoid. However, if the cavity quenches at this field level, the Q value would be degraded by a factor of two or possibly more. This might eventually require a temperature cycling of the cavity. Recommendations 1.Evaluate the impact of a potential factor of 2 degradation in Q, and consider a mitigation strategy for the fringe field, for example a cold magnetic shield around the cavity 12/10/2010I. Terechkine20 AAC Review, Nov , Closing Remarks: HINS Program

New Fringe Field Requirements Direct tests must be made to come out with a new number(s) for the allowed magnetic field. Test made so far were not conclusive. Improvement of the test setup is needed. A possibility of making the tests in the VTS needs to be considered. A new magnetic system must provide field up to ~2 kG in the spoke area so that the effect is clearly pronounced; hence superconducting coil must be used inside the spoke area. Initial study of the issue indicates that it is quite possible. 12/10/2010I. Terechkine21

Project X Linac Front End. SS0 Cryomodule. Focusing Lens. Requirements. Superconducting solenoid-based focusing lenses for the SS0 section of the linac front end are to be installed inside cryomodules with accelerating cavities. Number of the lenses in this section is (26 ? - to verify: S.N.). Number of spare lenses is to be stated (usually it is 10 – 20% of the total number, but also depends on the number of cryomodules with SS0 cavities). The number is needed ASAP to start worrying about strand procurement. Working temperature of the lenses is 2 K (1.8 K? 2.2 K? to agree with A. Klebaner). Nominal current must not exceed 200 A (to agree). The lenses must be designed with at least 25% current margin. Nominal focusing strength of the lenses is defined by the next expression: ∫B 2 dl = 1.8 T 2 ·m. (to verify: N. Soliak) Magnetic field generated by the lens on the walls of the nearest RF cavities not to exceed (10 µT ? 1 G ? 10 G ? - to verify: T. Kh.). Each lens must contain horizontal and vertical steering dipoles. Nominal bending strength of the dipoles ∫Bdl = 2.5·10 -3 T·m (to agree with S.N.). The dipoles must be designed with at least 50% field margin. Nominal current must not exceed 200 A. The magnetic field of the steering coils must be uniform in the aperture of the lens within +/- 10% - to verify. Required bore diameter of the lens is >30 mm (to verify with N. S.) Flange-to flange length of the lens not to exceed XXX mm.(to agree with S.N.). Focusing lenses must be designed in a way that allows application of a reliable quench protection technique and algorithm, which must be developed and tested. Cold mass of each lens must be equipped with gauges to measure its temperature and with voltage taps to register quench and to control quench protection equipment. Each lens must be tested using appropriate test stand for training purpose and also to check on the magnetic and quench performance. Each lens assembly must be installed on adjustable support allowing fine adjustments of the next coordinates: transverse horizontal and vertical movement range is +/- 3 mm; rotation relative to the transverse vertical and horizontal axis with the range of +/- 20 mrad; sensitivity of the adjuster must be better than ~20μm. Bellows in the beamline between the lens and the RF cavity must allow this motion range. Effective magnetic axis of each lens must be found and referenced to several fiducials installed on extension beams attached to the lens cold mass with ~0.1 mm accuracy. Design of the lens must be compatible with the design of the cryomodule for the SS0 section of the PX linac. Flanges of the lenses must correspond to the flanges of the RF cavities and a BPM installed near each lens. The lens assembly and alignment procedures must be developed and tested. 12/10/2010I. Terechkine22 Sept. 01, 2010