summary of accelerator systems collimation parallel session 19 october 2007 larp cm#9 - slac tom...
TRANSCRIPT
Summary of Accelerator Systems Collimation Parallel Session
19 October 2007
LARP CM#9 - SLAC
Tom Markiewicz/SLAC
BNL - FNAL- LBNL - SLAC
US LHC Accelerator Research Program
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 2 / 8
CRYSTAL COLLIMATION EXPERIMENTAT THE TEVATRON
Nikolai MokhovFermilab
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 CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 3 / 8
2005 Tevatron Experiment
(Analysis by V. Shiltsev)(Analysis by V. Shiltsev)
Channeled beam“peak” width is22±4 rad (rms)
With E03H out,LE033C BLM isproportional tonuclear interact.rate in crystal
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 4 / 8
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 100urad
Building a new goniometer with new specifications for motion tolerance and vacuum is needed
2 urad scan of channel May 26,2007
700
800
900
1000
1100
1200
1300
-2100 -2000 -1900 -1800 -1700 -1600 -1500 -1400 -1300 -1200
laser angle (urad)
loss
(h
z/vo
lts)
t:le033c t:le0pin 50 per. Mov. Avg. (t:le0pin) 24 per. Mov. Avg. (t:le033c)
150urad
320 urad
channelInto the beam
Angularmotion
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 5 / 8
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.
Noise on BLM signals
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 6 / 8
How to Meet Mission Goals?
Demonstrate high efficiency volume reflection seen in RD22 extraction line experiment in collider environment using EDGE of crystal
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 7 / 8
Plans for FY 2008: 3 Choices
Beam Studies: Nothing new, keep playing aroundContinue 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 goniometerStart 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
collaborationStart specifications and assessing new or additional beam diagnostics that will
be needed.
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 8 / 8
Tevatron Warm Space for New Hardware
antiprotons
E0
target
IR
proton s
D0
A0
collimator
IR
B0
C0
F0
Proton Set 1D49 Tar, E03 & F172 2nd Proton Set 2D171Tar, D173 & A0 Pbar Set 1F49 Tar, F48 & D172Pbar Set 2F173 Tar, F171 & E02
F171 collimator
E01 collimator E02 collimator
All these devices will have to be removedto accommodate space for new hardware
These locations have additional warm space but may not be optimal.
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 9 / 8
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 CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 10 / 8
COLLABORATION, LOI AND MEETING ON DEC. 6-7
Very encouraging support from• LARP management• Fermilab management• CERN management• INFN management• August Accelerator Advisory Committee at
Fermilab
It was proposed that we prepare a Letter-of-Intent (LOI), “Crystal Collimation Experiment at the Tevatron” and form an official collaboration.
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 11 / 8
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 CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 12 / 8
Rotatable CollimatorsJeff Smith
beambeam
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 13 / 8
Design of Jaw-Shaft-Mandrel
Cu coolant supply tubes twist to allow jaw rotation
Hub area
Glidcop Cu Mo
Cantilever Mo shaft @ both ends
Helical cooling channels
25mm below surface
20 facets
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 14 / 8
Design of Jaw Support and Rotation Mechanism
Triple CogGeneva DriveWheel required for 512 clicks per facet
U-Joint Flexes forShaft “sag” and “Slewing”
Water Cooling Inlet and outlet
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 15 / 8
Design Complete Except for RF Features
Jaw
Geneva Mechanism
Support Bearings
Worm GearShaft
Water CoolingChannel
U-Joint Axle
1-2mm Gap
Diaphragm
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 16 / 8
Current Vision of RF Transitions
Spiral style backing springs reside inside“Sheath” (sheath not shown)
Thin sheet metal RF “Curtain”
Round to Square TransitionTransition “Socket”
Spherical profile “Fingers”
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 17 / 8
Up Beam end detail view away from beam side
Spring flexes to maintain contact force on “Fingers” for longitudinal and lateral displacements of the Jaw ends
2 cam buttons (not shown) lift “Socket” off “Fingers” during Jaw rotation and rest in detents during collimation
Jaw cooling return line
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 18 / 8
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 19 / 8
Braze Test#2 Delivered 19 Dec 2006
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 20 / 8
Vacuum Bake of Braze Test#2 Results: 4/1/07~3x over LHC Spec
1st Jaw Braze Test Assembly has been vacuum baked at 300 degrees C for 32 hours.
•LHC Requirement = 1E-7 Pa = 7.5E-10 Torr•Baseline pressure of Vacuum Test Chamber:
4.3E-7 Pa (3.2E-9 Torr)•Pressure w/ 200mm Jaw Assy. in Test Chamber: 4.9E-7 Pa (3.7E-9 Torr)•Presumed pressure of 200mm lg. Jaw Assy.:
6.0E-8 Pa (4.5E-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 CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 21 / 8
6/25/07-7/2/07 Slice & Dice Braze Test#2
∙ 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
Interior slice: polished & etched
∙ Same fracturing patterns as in other slice∙ Braze of cooling coils to jaw ID good∙ Braze of cooling coil bottom to mandrel so-so
Longitudinal slice
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 22 / 8
Braze Test #3: Vacuum tests
•3rd 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.
Old New
Baseline 3.2E-9 Torr 2.4E-9 Torr??
w/ jaw assy. 3.7E-9 Torr 3.4E-9 Torr
Presumed jaw assy. pressure
4.5E-10 Torr 10E-10 Torr??
LHC requirement
7.5E-10 Torr 7.5E-10 Torr
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 23 / 8
Braze Test #3: Sectioning & ExaminationCu grain boundary cracking during brazing
Specimen 140mm OD x 60mm ID x 200mm 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 testedConcerns- Effect on performance- What happens in accident case?
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 24 / 8
Glidcop Al-15 Heat sampleWhile 1st 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 CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 25 / 8
Apr 6: Cu-Mo Hub Braze Test Assembly after 3 additional heat cycles (to mimic full assembly procedure) then
sectioned. Cu “finger” fractured
Small holes held braze wire
•Grain boundary issues?•Possible fracturing?
Cu-Mo joints we care about
1mm expansion gap
Samples sliced & polished and sent to Physical Electronics lab for analysis 4/23:Fractures evident
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 26 / 8
Compression fit for Cu-Mo joint
• Another option is to use a compression fit and diffusion bonding.
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.
Test hub fell apart once we made a slice!
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 27 / 8
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 CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 28 / 8
Molybdenum Half Shafts & Copper Hub Halves braze preparations
Expander PlugRetainer Ring
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 29 / 8
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 CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 30 / 8
Fixture for stacking 16 24cm-long quarter round jaws on full 960mm
cooling coil wrapped mandrel(mostly catalog parts: ordered)
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 31 / 8
Up Beam Flex Mount Assembly showing Ratchet and Actuator
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 32 / 8
Up Beam Flex Mount Assembly showing Ratchet and Actuator
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 33 / 8
Agreement in Progress to Buy a damaged “TCS1” collimator and stand from CERN
LARP CM9 - 19 October 2007 Collimation Summary - T. MarkiewiczSlide n° 34 / 8
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 (200mm Cu) and examine –apply lessons
Braze test #3 (200mm Cu) – apply lessons learned
Fab/braze 930mm shaft, mandrel, coil & jaw pieces
2008-01-01 1st full length jaw ready for thermal tests
Fab 4 shaft supports with bearings & rotation mechanism
Fab 2nd 930mm jaw as above with final materials (Glidcop) and equip with rf features, cooling features, motors, etc.
Modify 1st jaw or fab a 3rd jaw identical to 2nd 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 (“RC1”)
Modify RC1 as required to meet requirements
2009-01-01 Final prototype (“RC2”) fully operational with final materials, LHC control system-compatible, prototype shipped to CERN to beam test