A new 2 stage collimation design with new “L” shaped collimators.

Fermilab Tevatron Collimator
FNAL-Tevatron
Experience
Dean Still
April 14, 2005
Fermilab – Tevatron Department
Cern 2005

Tevatron Collimator Experience
• Introduction:
– Tevatron Machine Parameters
– Overview Tevatron Collimator System
• Halo Removal Performance
• Protecting Against Abort Kicker Prefires
• Collimators , Quenching and Damage
FNAL-Tevatron
Cern 2005

Tevatron Machine Parameters
Injection Energy
Flattop Energy
Number of bunches
Particles per bunch
Total Beam Intensities at 150, 980
Gev
Orbits Types
Lowbeta steps
Beta *
Number of IP’s
Shot setup (Fill) time
Store lengths
FNAL-Tevatron
150 Gev
980 Gev
36 proton & 36 antiproton
220-260 E9 protons & 30-50 E9 pbars
Protons 1E13 , 9E12
Antiprotons 1.6 E12, 1.4E12
Both beams in 1 vacuum pipe ; Beams
separated by electrostatic separators
15 different lattice in 25 steps
1.7m and transition to 35cm
2 : CDF & D0
2 hours
~ 30 hours
Cern 2005

Tevatron Collimator Overview
Motivation for Collimators for Collider II Run.
• Collider I System was:
– Slow motion controls.
– not a 2 stage collimator system.
– done completely manually and took 30 min
• Collider II System desired:
– A Halo Removal system only- To reduce losses at IP’s.
– A new 2 stage collimation design with new “L” shaped
collimators.
– An automated system that could be initiated by Collider
Sequencer software.
– Halo removal had be complete in 5 -10 min.
FNAL-Tevatron
Cern 2005

Tevatron Collimator for Halo Removal
New System Build 4 new Targets and 12 new 1.5m Collimators
for Halo Removal
Amplitude
yx ()
1.5 1.5
yminx ()
ymaxx ()
1
0.5
0
0.5
1
Target
@ ~5σ
Collimator
@~6σ
FNAL-Tevatron
2 Stage Collimator System
Collimator
Scattered
trajectories
−1.5
1.5
45 0 45 90 135 180 225 270 315 360 405
−45 x
Phase Adv. (degrees)
405
C0
B0
IR
protons
D0
IR
Proton Set 1
D49 Tar, E03 & F172
2nd
Proton Set 2
D171Tar, D173 & A0
Pbar Set 1
F49 Tar, F48 & D172
Pbar Set 2
F173 Tar, F171 & E02
A0
Cern 2005
antiprotons
target
collimator
E0
F0

Tevatron Shot Setup Process
Inject 36 final
protons
Open Helix &
Inject 9 Trans
of 4 Pbar bunches
Accelerate
Goto Lowbeta
Remove Halo
FNAL-Tevatron
Cern 2005

Collimator Moving Order for Halo Removal
Collimators move under 2 types of feedback:
1) Loss monitor Feedback
2) Beam intensity and Loss monitor feedback
1 2 3
4
Move to Poised
Position
N*s
FNAL-Tevatron
p
Fine Scrape Beam-Coll Pull back for
Parallel
Calibration
Store
p
coll
p
Sequence in Time of Collimator movement for Halo Removal
N*s
p
5
Cern 2005
Prepare for next
sequence
Time
p

Proton & Pbar Targets moving during Halo Removal
FNAL-Tevatron
Proton bunched beam intensity
Pbar bunched beam intensity
F49 local BLM
D49 local BLM
BLM Stop Limit
Remove .5% of proton beam
Cern 2005

Collimator Controls Hardware
Local Loss Monitors
used for pbar losses
F17
Spool
F171 F172
Collimator Collimator
FNAL-Tevatron
F17
Kicker
Protons
Local Loss Monitors
used for proton losses
F173
Target
F17
Dipole
VME based processor to conduct fast feedback
Cern 2005

Collimator Controls Block Diagram
C48
Sequencer
FNAL-Tevatron
init
abort
set
OAC is a Central Process
that orchestrates global
movement of all collimators
across 4 Front Ends
BPM
LATTICE
FLYING WIRE
read
OAC
calc xi(N,seq,ect)
T:CCTLXX[NUM_COL]
V:TEVCOL
Coll FE(n)
read/set
seq map
process
read set V:TEVCOL
coll status T:XXXenable - verify
T: (mode) T:(mode) - go
read state
mdat
tclk
mcast
Local Parameters[NUM_COLL]{
xi [NUM_SEQ] sq
xo[NUM_SEQ] NL
dx[NUM_SEQ] PL
dt[NUM_SEQ] Loss[NUM_SEQ]
Mode[NUM_SEQ]
enable[NUM_SEQ]
Collimator
Application
read
status
map
manual
control
graphics
read/set
coll
local
params
Cern 2005

Tevatron Collimator Experience
• Introduction:
– Tevatron Machine Parameters
– Overview Tevatron Collimator System
• Halo Removal Performance
• Protecting Against Abort Kicker Prefires
• Collimators , Quenching and Damage
FNAL-Tevatron
Cern 2005

Halo Loss Reduction Facto
100.00
90.00
80.00
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
FNAL-Tevatron
Halo Removal Efficiency
Halo Removal Efficiency (Protons)
1000 1500 2000 2500 3000 3500 4000
7/2002 1/2005
Store #
CDF Protons D0 Protons
1000.00
900.00
800.00
700.00
600.00
500.00
400.00
300.00
200.00
100.00
CDF Halo loss reduced ~ 10
D0 Halo loss reduced ~ 1 until
Vacuum and alignment improvements
Halo Loss Reductio
0.00
Halo Removal Efficiency (Anitprotons)
1000 1500 2000 2500 3000 3500 4000
Store #
CDF Anitprotons D0 Antiprotons
CDF Halo loss reduced ~ 20
D0 Halo loss reduced ~ 100
Cern 2005

Halo Loss ( loss (hz)/intensity (1E9))
10.00
9.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
CDF & D0 Halo Loss vs. Store
1000 1500 2000 2500 3000 3500 4000
FNAL-Tevatron
Store #
CDF Protons CDF Anitprotons D0 Protons D0 Antiprotons
Cern 2005

• Success
Halo Removal Comments
– New 2 stage design has proven to work with
good efficiency.
– Automation process to Halo Removal very easy
and reliable
• Adapting
– The Double scrape: Collimators stopping
prematurely.
– Alignment of Collimators; only checked 3 times
a year
FNAL-Tevatron
Cern 2005

Halo Removal Comments- Continued
• Problems
– Quenching while scraping - Providing a Post-
Mortem account in the Collimator Front end.
– Quenching due to automating Halo Removal.
Date
March 2002
March 2002
March 2005
March 2005
March 2005
FNAL-Tevatron
Lost Store Comment
Lost store at Halo removal due to mech stand failure
Lost store at Halo removal due to mech stand failure
Lost store at Halo removal due to D17 ahead of D49
Lost store at Halo removal due to FE bug
Lost store at Halo removal due to FE bug
Cern 2005

Tevatron Collimator Experience
• Introduction:
– Tevatron Machine Parameters
– Overview Tevatron Collimator System
• Halo Removal Performance
• Protecting Against Abort Kicker Prefires
• Collimators , Quenching and Damage
FNAL-Tevatron
Cern 2005

History of Abort Kicker Prefires
FNAL-Tevatron
Prefire Collimators Not installed
Collider Run I Prefires
Cern 2005

Addition of A48 Collimator to Protect
against A0 abort kicker prefires
FNAL-Tevatron
Add .5 m
Collimator
at A48 to shield
against prefires
C0
B0
A11V collimator
Already in place
IR
protons
D0
IR
A0
Cern 2005
antiprotons
target
collimator
A0 proton abort
kickers
E0
F0

A0 Kicker Transient Recorder
P8 P10 P12
P7 P9 P11
AAK1 prefire kicks 6 bunches
To To CDF.
FNAL-Tevatron
Antiproton Abort Kickers
12 12
7
Bunches hitting
the the A0 A0 abort block
Proton Abort Kickers
Cern 2005

A49 Loss Paddle for Prefire 3-8-2005
CDF
A49
A49 Loss Paddle
A48 Collimator
A47
Protons
FNAL-Tevatron
P7 P12
AA marker
A49 Loss Paddle
A49 BPM Int.
A47 BPM Int.
Cern 2005
P7-abort
P8-Hit
P9-Hit
P10-Hit
P11-Hit
P12-Hit

A48U
FNAL-Tevatron
Quench Data
Cell
A48U
F48U
B15U
A48L
B15L
F48L
Line
Cycle
A48U is one of the fastest
quenches we have had.
0
0
2
8
9
9
Notice we did not quench A1
Cern 2005

Comments on Kicker Prefire and Collimators
• Tevatron did not originally design a collimator
system to protect against kicker prefires.
• Once the collimator was installed, it was hard to
tell if the prefired beam was hitting it.
• Once confident prefired beam hit the collimator,
may need to increase length to protect
downstream cold spool.
• Need a better post-mortem system to determine
where all kicked bunches went.
FNAL-Tevatron
Cern 2005

Tevatron Collimator Experience
• Introduction:
– Tevatron Machine Parameters
– Overview Tevatron Collimator System
• Halo Removal Performance
• Protecting Against Abort Kicker Prefires
• Collimators , Quenching and Damage
FNAL-Tevatron
Cern 2005

Collimators, Quenches and Damage
• December 5, 2003
– First learned of a new category of quench called a
“Fast Quench”
– A Roman Pot moved into beam due to a controls
error causing beam loss damaging 2 collimators and
2 spool pieces (3 correction elements)
C18 spool E03 1.5m collimator D49 target
FNAL-Tevatron
Cern 2005

A48 Bus Drawing – Fast Quench
Pot 3 location
FNAL-Tevatron
Protons
A48U quenching dipoles: Looses current
At .5A/msec before the abort fires
Cern 2005

FNAL-Tevatron
QPM Over Sample Buffer
16msec
Quench A48 1st Abort Fired
Quenched 5 dipoles at A48; DI/Dt = .5A/msec
Development of
Quench:
A48U 16msec
D48L 13.5msec
F17L 13msec
E11U 12.5 msec
Cern 2005
Before abort
(Courtesy D. Wolff
& EE Support)

July 8,2004 – B11 Horizontal Separator Spark
Quench Estimate of Orbit growth w/ QPM Fast Abort
Fast
Quench
FNAL-Tevatron
(mm)
(mm)
10
10
8
8
6
6
4
4
2
2
-4
-4
-6
-6
-10
-10
Hor orbit for F48 kick due to F4 Quench
Hor orbit for F48 kick due to F4 Quench
2 msec after quench
2 msec after quench
0
0
0 20 40 60 80 100 120
-20
20 40 60 80 100 120
-2
Resulting -8Orbit
-8
Due to fast quench
Ring BPM location
Ring BPM location
Fast QPM abort would
have stopped quenches in
4 other houses
Cern 2005
Displacement @ # msec
Displacement @ # msec
real orbit
real orbit
diff sim-real
diff sim-real

Minimum Level to
Set BLM abort level
BLM Plot from December 5 Quench
FNAL-Tevatron
Fast quench could have been detected
Dipole at d4 could have pulled abort
Abort Kicker fired
Cern 2005
1 frame=2msec

Tevatron Ring Wide Loss Plot (Dec 5)
FNAL-Tevatron
Cern 2005

FNAL-Tevatron
Comments on Fast Quench
• Tevatron masks all BLM inputs during a store
due to very high probability of false abort.
• Fixed the Fast Quench by QPM code; over
sample and detect a large quench. Pulls abort
within 2msec instead of 16msec.
• BLM upgrade is in the works to gain additional
protection.
• Host of mechanisms to create fast quench
– Separator sparks
– Motion controlled device, Vacuum values, pots,
mirrors for sync light, collimators
Cern 2005

Comments on Fast Quench- Continued
• May 15, 2004 – Unknown
cause – Damaged E03
collimator again
• With a scan found it
damaged and ran 3 months
with it damaged.
FNAL-Tevatron
Cern 2005

FNAL-Tevatron
Summary
• Collider II Halo removal system has worked well as far as halo
removal efficiency and automatic process.
• Still working on improving collimator and post –mortem system for
abort kicker prefires.
• Dec 5,2003 quench and damage was “wake up call” to rethink
Tevatron beam loss protection.
• Learned details of new category of “fast quenches”.
• Implemented new QPM code to abort on detection of quench within
1-2msec, instead of 16msec. But still mask BLM during stores due
to false aborts.
• Reviewed all motion controlled devices with appropriate Abort.
– Vacuum abort upgrade done.
– Pot motion upgrade done.
• Insufficient process for gathering systematic and automatic data for
analyzing past quenches involving beam loss. Working on better
record keeping of data for every quench.
• Provided input to new BLM system coming in 2005.
Cern 2005