Mu2e Muon Beamline Vacuum Overview

1. Mu2e Muon Beamline Vacuum Overview Dave Pushka Mu2e Muon Beamline Vacuum Level 3 Manager 9 Feb 2017

2. Outline of Items Covered in this Review Presentation: • Orientation • Key Requirements • Overview of the Geography of the Production Solenoid (PS) and Detector Solenoid (DS) and the Transport Solenoid (TSu and TSd) • Piping and Instrumentation Diagram (P&ID) • Outgassing Methodology & Gas Load Summations for upstream muon beamline vacuum volume and downstream muon beamline vacuum volumes • Pie Charts of Gas Loads for upstream and downstream volumes • What is missing from the Outgassing Summation? • Hand Calculations for upstream and downstream muon beamline vacuum volumes • MOLFLO+ methodology • MOLFLO+ Results for the Upstream MB vacuum volume (a.k.a PS + TSu) • MOLFLO+ Results for the Downstream MB vacuum volume (a.k.aTSd + DS) • Interfaces and Physical Equipment Arrangement (locations of vacuum pumps). • Schedule Slide • Initial Evacuation • Simultaneous Initial Evacuation of the upstream and downstream MB vacuum volumes • Contamination and Diffusion Pump Oil • Vessels and Safety Conformance • Thin Windows • Interlocks, FEMA • Repressurization • Back-Up Material (FEM Risk Assessment, Key Outgassing Rates, Catalog Cuts, Performance Curves) Dave Pushka | Muon Beamline Vacuum Overview

3. Requirement Document and Summary of the Requirements: • Mu2e docdb document 1481 provides the requirements for the muon beam line vacuum, which include the key items: • Required pressure levesl: • PS + TSu (Upstream); ≤1 x 10-5torr. • TSd + DS (Downstream); ≤1 x 10-4torr (assuming the tracker and calorimeter achieve their gas load requirements) • Required vacuum pump down time: • ~ 100 hours. • Required pre-operational cleanliness: • standard high vacuum cleaning and degreasing. • Required operational cleanliness: • minimize, but not eliminate vacuum pump oil back-streaming. Dave Pushka | Muon Beamline Vacuum Overview

4. Over View of the Geography: Downstream Vacuum Mu2e 0,0,0 & pbar window Upstream Vacuum Downstream Vacuum Pumps Upstream vacuum pumps Dave Pushka | Muon Beamline Vacuum Overview

5. Over View of the Geography: Dave Pushka | Muon Beamline Vacuum Overview

6. Hardware Deliverables for Muon Beamline Vacuum: Mechanical Roughing & Backing Pump Vacuum By-Pass Line Production Solenoid End Cap And High Vacuum Pump out Line Mechanical Roughing & Backing Pump Vacuum Pump Spool Piece, VPSP Instrumentation Feed Through Bulkhead, IFB Dave Pushka | Muon Beamline Vacuum Overview

7. Context Material - Mu2e & Past Large Vacuum Experience: Dave Pushka | Muon Beamline Vacuum Overview

8. Details of the View of the Areas in the Upstream (PS+TSu): Pump out Line Bore PS-TS and TS-TS Interface Area COL 1 and 3u Dave Pushka | Muon Beamline Vacuum Overview

9. Details of the View of the Areas in the Downstream (TSd+DS) Vacuum Volume: Tracker, Calorimeter, Absorbers not shown, but estimates of gas loads are used in MOLFLO+ model Muon Beam Stop Detector Solenoid VPSP IFB Col 5 TSd Col3 Dave Pushka | Muon Beamline Vacuum Overview

10. Piping And Instrumentation Diagram (P&ID) from 6489: Dave Pushka | Muon Beamline Vacuum Overview

11. Outgassing and Vacuum Calculation Methodology: • Sum up the surface areas exposed to muon beamline vacuum • Assign material (SS, Al, Ti, W, fiberglass tape, etc) • Estimate temperature. • Assign outgassing rate for temperature at time = 1hour, 10 hours, etc. • Using achievable surface conditions • For example, the HRS is not likely to be ultra sonically washed, dried, baked and never touched by human hands again • Calculate gas load, Q = outgassing rate * area for various times • Determine pressure ignoring geometry (1 large volume) P=Q/S • Assign Outgassing to model in MOLFLO+ such that the total gas load matches the sum of the Area* Outgassing Rate for the real volume. • MOLFLO+ Surface areas are smaller than actual areas, but cross sectional areas are very similar. • Determine pressure as a function of location. Dave Pushka | Muon Beamline Vacuum Overview

12. Outgassing Gas Load Values: • Have reasonable outgassing numbers for everything in the PS+TSu. • Have reasonable outgassing numbers for surfaces and materials in the TSd+DS with the except of the Tracker and Calorimeter and the associated cabling and services. • For the tracker, the requirement on the gas load is ≤0.08 torr-l/s, and that is thevalue adopted for this analysis • Solid Model for Tracker is available and has been checked w.r.t. the requirement document values • For the calorimeter, an estimate of the outgassing load has been extracted based upon the surface area and materials expected in the calorimeter • The details of the calorimeter are still being refined • The long term gas load of the calorimeter is required to be negligible compared to the tracker gas load requirement of ≤0.08 torr-l/s • Outgassing rates come from literature (Elsey, Dayton, Santler, etc.) See the next few slides: Dave Pushka | Muon Beamline Vacuum Overview

13. Outgassing Summations for the Upstream Volume (Spread sheet on docdb document 6470): Dave Pushka | Muon Beamline Vacuum Overview

14. Outgassing Summations for the Downstream Volume (Spread sheet on docdb document 6470): Dave Pushka | Muon Beamline Vacuum Overview

15. Sources of Upstream (PS+TSu) Outgassing Gas Loads: Dave Pushka | Muon Beamline Vacuum Overview

16. Sources of Downstream (TSd+DS) Outgassing Gas Loads: Dave Pushka | Muon Beamline Vacuum Overview

17. Hand Calculation Upstream (PS+TSu): • Requirement document; P = 1 x 10—5 torr at 100 hours for PS. • Pump is 20,000 l/s (only 1 runs, other hot stand-by) • Lose 50% in angle valve • Lose 50% in baffle (cold trap) for non-condensable • 1/S net = (1/S pump + 1/S trap + 1/S valve + 1/S tee not in molflo) • Neglects contribution of cold trap pumping of water vapor, refrigerant, etc. • Assumes gas load from leaks is negligible Dave Pushka | Muon Beamline Vacuum Overview

18. Hand Calculation for DS+TSd: • Requirement document; P = 1 x 10—4 torr at 100 hours for DS. • Pumps are 8,000 l/s each • (Using 2 pumps, space for 4 available) • Lose 50% in angle valve • Lose 50% in baffle (cold trap) for non-condensable • 1/S net = (1/S pump + 1/S trap + 1/S valve) • Neglects contribution of cold trap pumping of water vapor, refrigerant, etc. • Assumes gas load from leaks and feed throughs is negligible Dave Pushka | Muon Beamline Vacuum Overview

19. MOLFLO+ Methodology: • A simplified model is created in NX of the PS+TSu or the TSd+DS • Circular cross sections modeled as 20 sided polygons to reduce the # of facets. • Solid material in NX = Vacuum, Voids in NX model represent solid material in MOLFLO+ • Write out .stl file as a text file, edit in notepad and save as a .stl • Read into MOLFLO+ (select units, clean up facets, etc.) • Measure area of the facets. • Apply uniform outgassing rate (in mbar-l/sec-cm2) to all the facets Dave Pushka | Muon Beamline Vacuum Overview

20. MOLFLO+ Run for baseline configuration: PS+TSd 1 pump with Baffle and valve Dave Pushka | Muon Beamline Vacuum Overview

21. MOLFLO+ Run for baseline configuration:Upstream Muon Beamline Vacuum Volume 3 x 10-8 torr-l/sec-cm2 average gas load (10 hour gas load), 4731 l/s net pump speed: This run made with 4731 l/s. A more precise estimate of net pump speed is 4826 l/s). 3x 10-8 torr-l/sec-cm2outgassing rate= the PS gas load @ 10 hours / MOLFLO+ model area. Ptarget = 4.7 x 10-6 torr Dave Pushka | Muon Beamline Vacuum Overview

22. MOLFLO+ run for one alternate PS +TSu configuration using 2 pumps: Alternate with two pumps with cold traps (9652 l/s): This run made with 10,000 l/s Not much gain compared to 1 pump due to conductance limit in the pipe. Dave Pushka | Muon Beamline Vacuum Overview

23. MOLFLO+ run for baseline configuration:Downstream Muon Beamline Vacuum Volume Dave Pushka | Muon Beamline Vacuum Overview

24. MOLFLO+ run for Downstream (TSd+DS) design configuration: Gas load = 2 x 10-7 mbar-l/cm2-s. Same methodology as used on the PSTwo pumps with cold traps (each @ Speed = 2666 l/s): Pressure along a facet along the length of the detector solenoid. 0 is at the TSd 100 is at the IFBClearly shows pressure gradient along bore due to tracker and calorimeter. P at TSU = 7.84 x 10-5 mbar P at TSU = 5.88 x 10-5torr P min = 4.75 x 10-5torr Dave Pushka | Muon Beamline Vacuum Overview

25. Summary of Meeting Requirement for Pressure Levels: • Recall, vacuum requirements are: • Required vacuum level: • PS + TSu (Upstream); ≤1 x 10-5 torr. • TSd+DS(Downstream); ≤1 x 10-4 torr. • Required vacuum pump down time: • ~100 hours. • Calculated Vacuum Performance for each are is: • Upstream (PS+TSu) P = 3.3 x 10-6 torr by hand calculations • Upstream (PS+TSu) P = 4.7 x 10-6 torr by simulation • Downstream (TSd+DS) P = 6 x 10-5torr by hand calculations • Downstream (TSd+DS) P = 4.7 x 10-5torr by simulation • This meets the pressure level requirements. Dave Pushka | Muon Beamline Vacuum Overview

26. Interfaces: • Section 2 of Mu2e Document 1168 list on six pages every interface between the Muon beamline vacuum and every other portion of the project. See: https://mu2e-docdb.fnal.gov:440/cgi-bin/RetrieveFile?docid=1168&filename=Muon_Beamline_Interface_v3.pdf&version=3 • Key Upstream (PS+TSu) interfaces: • Heat and Radiation Shield (HRS) (End cap welds to the HRS) • Remote Handling (applies to flanges on the PS End Cap) • Key Downstream (TSd+DS) interfaces: • VPSP welds to the Detector Solenoid Inner Bore • VPSP needs internal rails that match the DS rails • Anti-proton stopping window (separates Upstream from Downstream muon vacuum volumes). • Everything Else: See next slide……. Dave Pushka | Muon Beamline Vacuum Overview

27. Interfaces: • Everything Else: • Controls (described later in this talk) • Building (electric power, chilled water, dry instrument air) • Building & Shielding (Space for equipment, routing of vacuum exhaust lines, routing of by-pass line) • Solenoid cryo (need LN2 for the cold traps, GN2 for backfill) • Accelerator (primary beam entrance and exit pipes) • Detectors • Gas loads (leakage, cabling, structure, etc.) • Feedthroughs (Instrumentation Feedthrough Bulkhead) • Detector utilities (cooling, calibration system, signal and power cabling) • Tracker Straw Differential Pressure • Rely very heavily on the Top Level Assembly (F10002515) for coordinating physical interfaces. Dave Pushka | Muon Beamline Vacuum Overview

28. Layout of the Remote Handling Room: Upstream vacuum pumps located in remote handling room. Vacuum pump exhaust will go thru coalescing filters, then to the air handling duct, then up the M4 beamline or outside depending on radiation safety input. Dave Pushka | Muon Beamline Vacuum Overview

29. By-Pass line connection PS+TSu and TSd+DS: • Downstream Vacuum pump exhaust to be routed outside of the building. • - Line routing not yet put into F10002515 • - Exhaust will be filtered prior to routing upstairs and out of the building. Dave Pushka | Muon Beamline Vacuum Overview

30. By-Pass line connection PS+TSu and TSd+DS: Dave Pushka | Muon Beamline Vacuum Overview

31. By-Pass line connection PS+TSu and TSd+DS Layout work in progress (these dimensions not used in calcs yet): Dave Pushka | Muon Beamline Vacuum Overview

32. Vacuum Seal Criteria: • Seals in the Upstream vacuum system inside of the PS endcap will be all metal, radiation hard seals where all welded construction is not practical. • Seals in the Upstream vacuum system inside of the remote handling room will be either all metal or a combination of elastomeric seal and all metal - requires radiation dose input which has not yet been finalized. • Seals in the Downstream vacuum system will be elastomeric. • Seals in the by-pass line (described in the following section) will be minimized by using all welded construction. Seals at the roughing pump ends will be elastomeric. Dave Pushka | Muon Beamline Vacuum Overview

33. Initial Evacuation Criteria: • Requirements provide a time constraint on the evacuation to operating pressure. • Working plan for Mu2e is to perform it in less than 1 shift • KTeV took about 1 hour. • NuMI took about 3 days. • Significant requirement is to keep the differential pressure across the pbar stopping window (located between the TSu and the TSd) to a fraction of what it can take • Pbar stopping window thickness determined by the physics requirement, not vacuum requirement • Working design tolerates >50 torr differential • More on this pbar window in the section on windows. Dave Pushka | Muon Beamline Vacuum Overview

34. Simultaneous Pump-Down of the Upstream and Downstream ends: PS roughing pump can be started in this range, which changes shape of red (PS) curve at times > 400 minutes Dave Pushka | Muon Beamline Vacuum Overview

35. Simultaneous Pump-Down of the Upstream and Downstream ends: PS roughing pump started here, which changes shape of red (PS) curve at times > 500 minutes DS roughing vacuum limited by the roughing line speed. – Future work to investigate and model larger sizing to get better vacuum. Desirable point to start diffusion pumps to minimize back steaming of oil (described next) 150 microns. Dave Pushka | Muon Beamline Vacuum Overview

36. Which diffusion pump oil to use? • Inputs (in order of importance): • Oil adverse affects on the detector • Must minimize adverse affects of pump oil on detectors • Desired operating pressure • No better than 10-6 torr is required. • Oil Back streaming rate • Must minimize oil backstreaming • Service Life • Radiation Resistance • Tolerance to Oxidation • Proper control, fail closed valves, etc. can reduce oxidation potential. • Cost Dave Pushka | Muon Beamline Vacuum Overview

37. Which diffusion pump oil to use? DC-702 (Mixture of phenylmethyl and dimethyl cyclosiloxane) • Resistant to oxidation/hydrolysis • Suitable for 10-5 range • While lower cost, may not be readily available DC-704 (tetraphenyl tetramethyl trisiloxane) • Best oxidation resistance • Suitable for 10-7 range • $500 per gallon DC-705 (pentaphenyl trimethyl trisiloxane) • Best ultimate pressure • Low back-streaming • $900 per gallon Octoil • $300 per gallon Santovac (Polyphenyl Ether) • Best ultimate pressure • Very low back streaming at High vacuum • Does not polymerize under ionizing radiation • > $2000 per gallon Likely our best choices. DC-704 equivalent preferred. Dave Pushka | Muon Beamline Vacuum Overview

38. When to Start the Diffusion pumps? • Crossover is normally between 5 x 10-2 torr and 1.5 x 10-1 torr (50 – 150 microns). • Below this range mechanical pumps are rapidly loosing efficiency and above this range the back streaming of oil from the diffusion pump increases. • From about 1 x 10-4 torr to the lowest achievable vacuum level of the system, the back streaming rate of a diffusion pump is independent of the inlet pressure. • Keep the period of inlet pressure exceeding 10-2 torr (10 microns) short, (on the order of a few tens of seconds). Extended operation at these pressures will result in unacceptably high amounts of oil back streaming into the vacuum system. • Traps minimize oil back streaming from the diffusion pump at high inlet pressure. For KTeV, the high vacuum valve was opened when the chamber was pumped to less than 10-1 torr (50 to 100 microns – blowers have an ultimate of about 30 microns). • Diffusion pumps were on, hot, foreline connected to the roughing pump, but isolation valve closed. • For KTeV, the vessel pressure rapidly fell – and in about 1 minute, the chamber pressure was in the 10-5torr range. • Therefore, start the Mu2e diffusion pumps in a very similar manner – with vessels as close to 5 x 10-2(50 microns) as possible. But distance to the roughing pump and gas load may make 50 microns hard to do. Roughing line dimensions will be maximized. Dave Pushka | Muon Beamline Vacuum Overview

39. Estimate of the Oil Back streaming in the Upstream (PS+TSu) and Downstream (TSd+DS): Based on published data from Leybold using LEYBONOL LVO 500 (a plain mineral oil) diffusion pump oil. Silicon oil (DC-704 or 705 equivalent) should have lower back streaming rates. Dave Pushka | Muon Beamline Vacuum Overview

40. Back Streamed Diffusion Pump Oil Where Does it Go? • Prediction based on manufacturer’s data for back streaming of plain mineral oil is less than a shot glass of oil for 3 years operation. • The silicone oils are reported to have lower back streaming rates, but I’ve not found a quantified value. • From KTeV, using un-trapped diffusion pumps, there was evidence of oil on the bottom of the vessels where the pumps were located. • Oil film on the vessel bottom made walking difficult. • Oil evidence diminished dramatically as distance from the pumps increased. • Conclusion is that the oil sticks to the first surface it hits, then runs down the vessel walls and collects at a low point. Dave Pushka | Muon Beamline Vacuum Overview

41. Back Streamed Diffusion Pump Oil Where Does it Go for Mu2e? • Upstream (PS+TSu): • Diffusion pump oil will most likely hit the high vacuum pump out line, or angle valve. Calculate 99.76% of the oil will hit the high vacuum pump out line. • Should consider slightly sloping high vacuum line to drain back to the diffusion pump inlet so that the oil returns to the pump. • 0.329% (0.12 ml for three years operation based on mineral oil pump fluid) will hit the PS End Cap. • Expectation is that the oil will stick to the PS end cap and collect at the bottom (just like in KTeV). • Should consider including a small drain in PS end cap • No line of slight to the target exists. • Do not expect the target to ‘see’ any measurable diffusion pump oil. Dave Pushka | Muon Beamline Vacuum Overview

42. Back Streamed Diffusion Pump Oil Where Does it Go for Mu2e? • Downstream (TSd+DS): • Diffusion pump oil will most likely hit the angle valve and VPSP nozzle. Calculate 84% of the oil will hit the angle valve or nozzle. • Should consider slightly sloping VPSP nozzles to drain back to the diffusion pump inlet so that the oil returns to the pump. • 16% (5.18 ml for three years operation based on mineral oil pump fluid) will make it into the DS vacuum space. • Expectation is that the oil will hit the Muon Beam Stop (MBS). • No line of slight to anything upstream of the MBS. • Do not expect the calorimeter or tracker or anything upstream of the MBS to ‘see’ any measurable diffusion pump oil. Dave Pushka | Muon Beamline Vacuum Overview

43. Back Streamed Diffusion Pump Oil, But what if some oil got on Detector Items? • Silicone Diffusion pump oils are: • Electrically non-conductive. • A coating on an electronics board will not cause a short circuit. • Transformers operate immersed in a similar oil polydimethyl siloxane. • Non-Reactive • Specifically engineered to be non-reactive • Do not self polymermize • Reaction with straw tube material can be tested to verify these fluids are not damaging • DC-704 is tetraphenyl tetramethyl trisiloxane C28H32O2Si3 MW = 484.81 • Dc705 is pentaphenyl trimethyl trisiloxane C33H34O2Si3 MW = 546.88 Dave Pushka | Muon Beamline Vacuum Overview

44. Diffusion Pump Oil Quality Monitoring • Diffusion Pump Oil is subject to ‘cracking’ when exposed to oxygen when hot. • Silicon diffusion pump oils are the most cracking resistant. • DC-704 diffusion pump oil from KTeV never showed evidence of cracking. Color remained water clear. • If a serious mis-operation occurs, oil will need to be changed. • A non-trivial effort • Upstream end requires radiation analysis • Downstream end requires opening the CRV and External shielding • Fail closed valves and PLC logic to prevent inadvertent operational errors worked well on KTeV to maintain diffusion pump oil quality. – Expect to do the same for Mu2e. Dave Pushka | Muon Beamline Vacuum Overview

45. Keeping the muon beamline (relatively) clean? • Assume solenoid inner bores are not cleaned for vacuum service upon receipt from GA or TD, but meet the FNAL cleanliness specifications • Assume HRS is not cleaned for vacuum service upon receipt – cleaned upon receipt. • Assume PS End Cap, VPSP, IFB are not cleaned for vacuum service upon receiptfrom vendor / fabricator – these to be cleaned by FNAL upon receipt • Request Collimators (part of muon beamline) are assembled under clean conditions with minimal contamination from finger prints, and all parts are washed with soap and water, distilled water rinse, then Isopropyl alcohol (IPA) wipe and bagged prior to installation in the TS bore. • Clean (clean means: washed with soap and water, distilled water rinse, then Isopropyl alcohol (IPA) wipe and bagged with an HDPE plastic sheeting which is sealed closed. Apply to: • HRS after welding is completed to seal between HRS bore and PS • PS end cap prior to welding and after welding to HRS is complete • VPSP after welding is completed to join the DS and VPSP • TS warm bores after installation Dave Pushka | Muon Beamline Vacuum Overview

46. Keeping the muon beamline (relatively) clean? • Once Cleaned, Maintain Cleanliness by: • Covering All Open Ports with a metal blind flange or at least plastic sheeting. • Purge with clean, dry air if possible. • Biggest source of gas load is in the Downstream (TSd+DS) because of the detectors and non-solid, non-metal components including significant cabling. • Will need to work with the detector people to: • Keep cabling clean, free from skin oils and general dirt. • Keep detector train covered when outside of DS • Minimize contamination since contamination = gas load • Etc. Dave Pushka | Muon Beamline Vacuum Overview

47. Summary of Meeting Requirement for Cleanliness: • Recall, Cleanliness requirements are: • Required pre-operational cleanliness: • standard high vacuum cleaning and degreasing. • Required operational cleanliness: • minimize, but not eliminate vacuum pump oil back-streaming. • We can meet the requirements for the Cleanliness Levels as long as we are careful, perform the work, and allow sufficient time for doing a complete cleaning. • We also need significant help from the solenoid, detector, magnetic field measuring and electronics people to help achieve a clean system. Dave Pushka | Muon Beamline Vacuum Overview

48. Initial Pump down and Leak Testing (QA/QC): • Plan is to initially pump down the warm vacuum spaces prior to detector train installation. • Will perform helium mass spectrometry leak testing during the initial evacuation to locate and repair vacuum leaks. • May require several iterations to identify, find, and repair leaks to air. • Goal is to make the air leaks small with respect to the outgassing and tracker gas loads. • Then, second iteration to evacuate the Downstream (and the Upstream) with the Detector Train installed in the DS. Dave Pushka | Muon Beamline Vacuum Overview

49. Deliverable Vessels for the Muon Beam Line: • PS End Cap and Vacuum Pump-out Line: Dave Pushka | Muon Beamline Vacuum Overview

50. Deliverable Vessels for the Muon Beam Line: • VPSP and IFB: • VPSP modeled in Native NX (in TC) • IFB not yet modeled in Native NX (this image is from a STEP file): Dave Pushka | Muon Beamline Vacuum Overview