US LHC Accelerator Research Program BNL FNAL LBNL
US LHC Accelerator Research Program BNL - FNAL- LBNL - SLAC Summary of Accelerator Systems Collimation Parallel Session 19 October 2007 LARP CM#9 - SLAC Tom Markiewicz/SLAC LARP CM 9 - 19 October 2007 Collimation Summary - T. Markiewicz
CRYSTAL COLLIMATION EXPERIMENT AT THE TEVATRON Nikolai Mokhov Fermilab Mission Statement We propose an experiment at Fermilab’s Tevatron to measure the predicted improvement in collimation efficiency that could be obtained by replacing amorphous primary collimators with bent crystals. Considering the unique possibility provided by the Tevatron Collider, and having already established fruitful collaborative efforts on crystal characterization, tests and use for collimation, we propose to test and confirm models of multi-turn dynamics with crystals by exploiting channeling and newly understood phenomena such as volume reflection as well as to further study collimation. LARP CM 9 - 19 October 2007 2 Collimation Summary - T. Markiewicz
2005 Tevatron Experiment With E 03 H out, LE 033 C BLM is proportional to nuclear interact. rate in crystal Channeled beam “peak” width is 22± 4 mrad (rms) (Analysis by V. Shiltsev) LARP CM 9 - 19 October 2007 3 Collimation Summary - T. Markiewicz
2006 Installation of Shorter Crystal with Smaller Bend and 2007 Run/Analysis Original installation had misaligned crystal Angular reproducibility for a horizontal translation of the table terrible – 1 mil horizontal translation can produce an angle error of 100 urad Building a new goniometer with new specifications for motion tolerance and vacuum is needed Angular motion 320 urad 150 urad channel Into the beam LARP CM 9 - 19 October 2007 4 Collimation Summary - T. Markiewicz
Noise on BLM signals Other Issues with 2007 Run Noisy Losses on Detectors: Noisy losses produced on the PIN and BLM monitors look like channeling signatures. These are real effects caused by motion of the beam, effects of abort gap cleaning, etc. Solutions to these are refining operational procedures and attempting to build better orbit stabilization software around the area of the bent crystal. Improving Beam Diagnostic Capabilities – Current beam diagnostics used to detect channeled and VR beam is a PIN diode system and a Tevatron ionization style BLM. (picture in next slide) – The PIN diode is reasonable for detecting the rate of nuclear interactions at the crystal. – In order to view the channeled and VR beam downstream of the crystal better diagnostics are needed. Roman Pot style detectors have been considered and offered. LARP CM 9 - 19 October 2007 5 Collimation Summary - T. Markiewicz
How to Meet Mission Goals? Demonstrate high efficiency volume reflection seen in RD 22 extraction line experiment in collider environment using EDGE of crystal LARP CM 9 - 19 October 2007 6 Collimation Summary - T. Markiewicz
Plans for FY 2008: 3 Choices Beam Studies: Nothing new, keep playing around Continue to use the installed crystal assembly and strip crystal to demonstrate main goals. This may require more study time due to increased setup now that problems with goniometer have been characterized. Would like to have 2 to 3 of End of Store study periods as early as Dec. 2007 to demonstrate well characterized channeling from the strip crystal now that more is understood about the goniometer motion. New Goniometer(s): No new diagnostics, but replace goniometer Start specifications and engineering for new horizontal goniometer that would replace current assembly. Currently have identified a FNAL engineer to work on this. If full 2 plane crystal collimation is going to be demonstrated that would require an additional vertical goniometer to be built. A full simulation would be required for best placement of the vertical goniometer as well locations of channeled and volume reflected beams. Beam Diagnostics: The whole enchilada: Raison d’etre for collaboration Start specifications and assessing new or additional beam diagnostics that will be needed. LARP CM 9 - 19 October 2007 7 Collimation Summary - T. Markiewicz
Tevatron Warm Space for New Hardware E 01 collimator E 02 collimator F 171 collimator All these devices will have to be removed to accommodate space for new hardware Proton Set 1 D 49 Tar, 2 nd Proton Set 2 D 171 Tar, Pbar Set 1 F 49 Tar, Pbar Set 2 F 173 Tar, E 03 & F 172 D 173 & A 0 F 48 & D 172 F 171 & E 02 These locations have additional warm space but may not be optimal. LARP CM 9 - 19 October 2007 8 Collimation Summary - T. Markiewicz
Time Timing for Installing New Hardware: Should be stressed that any new hardware installed into the Tevatron for use in 2009 will have to be ready for the Summer 2008 shutdown. Ferrara needs 6 months minimum to fabricate goniometers and will not spend $/effort without FIRM COMMITMENT to run the experiment LARP CM 9 - 19 October 2007 9 Collimation Summary - T. Markiewicz
COLLABORATION, LOI AND MEETING ON DEC. 6 -7 Very encouraging support from • LARP management • Fermilab management • CERN management • INFN management • August Accelerator Advisory Fermilab Committee It was proposed that we prepare a Letter-of-Intent (LOI), “Crystal Collimation Experiment at the Tevatron” and form an official collaboration. LARP CM 9 - 19 October 2007 10 Collimation Summary - T. Markiewicz at
Immediate Requirement Need full realistic multi-turn simulations – for the current lattice and crystal/collimator configuration to confirm 1999 -2003 results, justify a choice of a short crystal and identify locations for comprehensive beam diagnostics (single particle tracking capability? ) and second (vertical) crystal/goniometer Can this happen in time for Dec 6 -7 Collaboration Meeting in sufficient detail to motivate invasive hardware installation, diagnostic construction and formation of a 50 -100 member international collaboration? 1) Nikolai & Sasha Drozhdin committed 2) Known to be needed in April 2007, but zero produced LARP CM 9 - 19 October 2007 11 Collimation Summary - T. Markiewicz
Rotatable Collimators Jeff Smith beam LARP CM 9 - 19 October 2007 12 Collimation Summary - T. Markiewicz
Design of Jaw-Shaft-Mandrel 20 facets Glidcop Cu Mo Cu coolant supply tubes twist to allow jaw rotation Helical cooling channels 25 mm below surface Hub area Cantilever Mo shaft @ both ends LARP CM 9 - 19 October 2007 13 Collimation Summary - T. Markiewicz
Design of Jaw Support and Rotation Mechanism U-Joint Flexes for Shaft “sag” and “Slewing” Triple Cog Geneva Drive Wheel required for 512 clicks per facet LARP CM 9 - 19 October 2007 Water Cooling Inlet and outlet 14 Collimation Summary - T. Markiewicz
Design Complete Except for RF Features Jaw Geneva Mechanism Worm Gear Shaft 1 -2 mm Gap Water Cooling Channel U-Joint Axle Support Bearings Diaphragm LARP CM 9 - 19 October 2007 15 Collimation Summary - T. Markiewicz
Current Vision of RF Transitions Spiral style backing springs reside inside “Sheath” (sheath not shown) Thin sheet metal RF “Curtain” Transition “Socket” Round to Square Transition Spherical profile “Fingers” LARP CM 9 - 19 October 2007 16 Collimation Summary - T. Markiewicz
Up Beam end detail view away from beam side 2 cam buttons (not shown) lift “Socket” off “Fingers” during Jaw rotation and rest in detents during collimation Jaw cooling return line Spring flexes to maintain contact force on “Fingers” for longitudinal and lateral displacements of the Jaw ends LARP CM 9 - 19 October 2007 17 Collimation Summary - T. Markiewicz
LARP CM 9 - 19 October 2007 18 Collimation Summary - T. Markiewicz
Braze Test#2 Delivered 19 Dec 2006 LARP CM 9 - 19 October 2007 19 Collimation Summary - T. Markiewicz
Vacuum Bake of Braze Test#2 Results: 4/1/07 ~3 x over LHC Spec 1 st Jaw Braze Test Assembly has been vacuum baked at 300 degrees C for 32 hours. • LHC Requirement = 1 E-7 Pa = 7. 5 E-10 Torr • Baseline pressure of Vacuum Test Chamber: 4. 3 E-7 Pa (3. 2 E-9 Torr) • Pressure w/ 200 mm Jaw Assy. in Test Chamber: 4. 9 E-7 Pa (3. 7 E-9 Torr) • Presumed pressure of 200 mm lg. Jaw Assy. : 6. 0 E-8 Pa (4. 5 E-10 Torr) • Note: above readings were from gauges in the foreline, closer to the pump than to the Test Chamber. Pressures at the part could be higher. Outcome: SLAC vacuum group has suggested longitudinal grooves be incorporated into the inner length of jaws; incorporated into next prototype LARP CM 9 - 19 October 2007 20 Collimation Summary - T. Markiewicz
6/25/07 -7/2/07 Slice & Dice Braze Test#2 Interior slice: polished & etched Longitudinal slice ∙ Evidence of fracturing along grain boundaries presumed due to too-rapid cooldown after braze - areas near ends and OD look better ∙ Braze of jaws to hub GOOD ∙ 3 of 4 jaw-jaw brazes GOOD LARP CM 9 - 19 October 2007 ∙ Same fracturing patterns as in other slice ∙ Braze of cooling coils to jaw ID good ∙ Braze of cooling coil bottom to mandrel so-so 21 Collimation Summary - T. Markiewicz
Braze Test #3: Vacuum tests • 3 rd Jaw Braze Test Assembly has been vacuum baked at 300 degrees C for 32 hours. Results in slightly lower pressure. • Inclusion of longitudinal grooves in the inner length of jaws for better outgasing • Test Chamber setup similar to previous test. LARP CM 9 - 19 October 2007 Old New Baseline 3. 2 E-9 Torr 2. 4 E-9 Torr? ? w/ jaw assy. 3. 7 E-9 Torr 3. 4 E-9 Torr Presumed jaw assy. pressure 4. 5 E-10 Torr 10 E-10 Torr? ? LHC requirement 7. 5 E-10 Torr 22 Collimation Summary - T. Markiewicz
Braze Test #3: Sectioning & Examination Cu grain boundary cracking during brazing Specimen 140 mm OD x 60 mm ID x 200 mm L (¼ section shown) - one braze cycle in the 900 C range - grain boundary cracks located in interior regions - believed due to excessive heating rate - Glidcop to be tested Concerns - Effect on performance - What happens in accident case? LARP CM 9 - 19 October 2007 23 Collimation Summary - T. Markiewicz
Glidcop Al-15 Heat sample While 1 st jaw used to test thermal mechanical issues is Copper, first full 2 jaw prototype will use Glidcop 2 Heats (at Jaw brazing temperature) No grain boundary cracking is apparent Metallographic samples are being prepared for microscopic inspection LARP CM 9 - 19 October 2007 24 Collimation Summary - T. Markiewicz
Apr 6: Cu-Mo Hub Braze Test Assembly after 3 additional heat cycles (to mimic full assembly procedure) then sectioned. Cu “finger” fractured • Grain boundary issues? • Possible fracturing? Cu-Mo joints we care about 1 mm expansion gap Samples sliced & polished and sent to Physical Electronics lab for analysis 4/23: Fractures evident Small holes held braze wire LARP CM 9 - 19 October 2007 25 Collimation Summary - T. Markiewicz
Compression fit for Cu-Mo joint • Another option is to use a compression fit and diffusion bonding. Test hub fell apart once we made a slice! Copper Jaw is constrained on the outside diameter with Carbon and when heated to ~ 900 degrees C is forced to yield so that upon cooling to ~ 500 degrees C the inner diameter begins to shrink onto the Mo Shaft resulting a substantial interference fit. LARP CM 9 - 19 October 2007 26 Collimation Summary - T. Markiewicz
Cu-Mo joint: Segmented Moly for expansion • Another option is to use a segmented flexible molybdenum end to prevent fractures and prevent Co from pulling away from Moly. Will be cutting small samples for metallurgy tests. May make slight modifications for better braze joint LARP CM 9 - 19 October 2007 27 Collimation Summary - T. Markiewicz
Molybdenum Half Shafts & Copper Hub Halves braze preparations Retainer Ring Expander Plug LARP CM 9 - 19 October 2007 28 Collimation Summary - T. Markiewicz
21 Mar 2007: Full length Mandrel: In-House & Inspected – Now that shaft design complete, order to bore central hole made – Will wind with in-house copper tubing LARP CM 9 - 19 October 2007 29 Collimation Summary - T. Markiewicz
Fixture for stacking 16 24 cm-long quarter round jaws on full 960 mm cooling coil wrapped mandrel (mostly catalog parts: ordered) LARP CM 9 - 19 October 2007 30 Collimation Summary - T. Markiewicz
Up Beam Flex Mount Assembly showing Ratchet and Actuator LARP CM 9 - 19 October 2007 31 Collimation Summary - T. Markiewicz
Up Beam Flex Mount Assembly showing Ratchet and Actuator LARP CM 9 - 19 October 2007 32 Collimation Summary - T. Markiewicz
Agreement in Progress to Buy a damaged “TCS 1” collimator and stand from CERN LARP CM 9 - 19 October 2007 33 Collimation Summary - T. Markiewicz
LARP Collimator Delivery Schedule Done Braze test #1 (short piece) & coil winding procedures/hardware Prep heaters, chillers, measurement sensors & fixtures, DAQ & lab Section Braze test #2 (200 mm Cu) and examine –apply lessons Braze test #3 (200 mm Cu) – apply lessons learned Fab/braze 930 mm shaft, mandrel, coil & jaw pieces 2008 -01 -01 1 st full length jaw ready for thermal tests Fab 4 shaft supports with bearings & rotation mechanism Fab 2 nd 930 mm jaw as above with final materials (Glidcop) and equip with rf features, cooling features, motors, etc. Modify 1 st jaw or fab a 3 rd jaw identical to 2 nd jaw, as above Mount 2 jaws in vacuum vessel with external alignment features 2008 -09 -01 2 full length jaws with full motion control in vacuum tank available for mechanical & vacuum tests in all orientations (“RC 1”) Modify RC 1 as required to meet requirements 2009 -01 -01 Final prototype (“RC 2”) fully operational with final materials, LHC control system-compatible, prototype shipped to CERN to beam test LARP CM 9 - 19 October 2007 34 Collimation Summary - T. Markiewicz
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