TEVATRON IONIZATION PROFILE MONITOR Andreas Jansson Fermilab.
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Transcript of TEVATRON IONIZATION PROFILE MONITOR Andreas Jansson Fermilab.
TEVATRON IONIZATION PROFILE
MONITOR
Andreas JanssonFermilab
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 2
People
AD:C. RivettaL. ValerioJ. ZagelB. DysertC. Lundberg…
CD:M. BowdenR. Kwarciany D. Slimmer…
PD:A. BrossK. BowieH. NguyenT. Fitzpatrick…
Also help from: D. Harding (TD), V. Kashikin (TD), T. Zimmerman (PD), Z. Tang (PD), B. Hively (AD), the Tev Techs …
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 3
Talk outline
• Motivation for IPMs in Tevatron• Special challenges in Tevatron• Design of Tevatron IPMs• Tests• Pictures from “down under”.
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 4
Motivation
• Directly measure injection matching and emittance growth at injection
• Continuously measure emittance eg on ramp
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 5
IPM working principle
• Measure distribution of rest gas ionization by:– Drifting ions onto a
detector using an electric field, or
– Drifting ionization electrons onto a detector using a E||B field.
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 6
Challenge I – Small beam size
• Small beam size -> fine detector granularity (1/4 mm pitch)
• Three different positions due to helix -> need wide active area (~3 cm)
• Many channels (128)
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 7
Challenge II – Two beams
-15 -10 -5 5 10 15
-15
-10
-5
5
10
15
= 20 mm mradp/p = 7.5 10-4
X [mm]
Y [mm]Inj. old helixInj. new helixFlattop
One and threesigma contours
• Projected beam profiles may overlap
• Don’t trust to separate beams
• Separate by timing -> single bunch resolution!
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 8
Challenge III – Too good vaccum
• Gas pressure at E0 before 2004 shutdown was in low 10-8’s, slated to be improved
• Based on estimated gas composition (RGA scan), expect about 1000e/bunch for a 10cm detector at 3 108 Torr and 2.7 1011 protons/bunch.
• Need for a local vacuum bump after vacuum inprovements.
graph: F. Sauli, CERN 77-09
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 9
Challenge IV – Parasitic signals
• Measure extremely small signal (~fC) in the presence of very strong EM field from beam.
• Anode strip acts as electrostatic pick-up.
• Sharp resonaces require strong LP filtering, low time resolution.
0 1108
2108
3108
4108
5108
-140
-130
-120
-110
-100
-90
-80
-70
Beam to anode strip coupling measured on Booster IPM.
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 10
Fermilab QIE8 ASIC
• Charge Integrating Encoder (QIE)
• Developed at Fermilab• Used by KTeV, CDF, Minos,
CMS…• Frequency range 7-53 MHz• No deadtime.• LSB 2.6fC (16000e) in
logarithmic mode, 0.9fC (6000e) in linear mode
• Dynamic range >104 in logarithmic mode
• Can achieve noise of O(1fC)
• Radiation “tolerant”
5I
I
I
I
Signal Amp.
/ Splitter
5I
I
I
I
ReferenceAmp.
/ Splitter
Comparator and
Multiplexor
Sig. Input
Ref. Input
Range Encoder
FADC
C
C
5C
25C
C
C
5C
25C
State Machine 4(Reset Integrate Compare MuxOut)
Digitize
Mantissa
Range/Exponent
Cap. ID
2
2
5
A Choice of Two Amplifiers with
G= (-2.7) / (1)
design: T. Zimmerman
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 11
QIE simulations
• Injection is most difficult (fewer counts per channel).
• Signal per bunch is small, but gain limited by MCP saturation effects from total (proton) signal.
• Need about 300 primaries (per bunch) for 10% beam width accuracy (requires gas injection).
• Higher accuracy can be obtained by averaging many turns (ramp measurement).
simulations: H. Nguyen
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 12
Keeping the noise low
• To keep noise at minimum, digitize close to source (in tunnel).
• 128 channels 1 byte 15 MHz = 16 Gbit/s of data!
• Use high-speed serial links (on optical fiber)
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 13
QIE test stand
• Using laser based PMT test setup in Lab6
• KTeV test board modified with CMS-QIE
• Observed good linearity and insensitivity to clock phase
measurement: H. Nguyen
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 14
QIE quirks
• QIE input is NOT bipolar!
• Relatively mall pulse of wrong polarity can temporarily shut down the input– Beam EM pick-up yield
bipolar pulses– Cable reflections may
invert pulse polarity
• Limit diffuse, need to be careful
100 200 300 400 500 600Time ns-100
-50
0
50
100
pirtSlangisAu
110 8 210 8 310 8 410 8 5108
-200
-180
-160
-140
-120
-100
-60
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 15
Cable tests
• Stepping QIE clock phase w.r.t the incoming pulse, can improve time resolution
• Derivation of composite signal yields the original pulse
• Used to study reflections due to connectors in front-end cabling
measurement: C. Rivetta
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 16
Rad level measurements
• Reading 125 mrad/h during normal running at ~4.5 feet
• 18 years to 20 krad!
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 17
Component rad tests
• Tested commercial TI serializer in Tevatron tunnel for >200 days.
• Previously tested (by others) for total dose ~Mrad.
• Only handful of link errors seen.
• One latchup candidate, cleared by cycling power.
• Observed error rate should not affect operation.
0 50 100 150 200Days
1
10
100
1000
stnuoC
0 50 100 150 200Days
0
0.2
0.4
0.6
0.8
1
sutatS
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 18
MCP saturation
• MCP output current per unit area is limited by MCP pore recharge time.
• If hit rate per pore exceeds recharge time, output is reduced
• Onset of saturation observed in MI IPMs, as expected from calculations.
For Tev, will abandon Chevron configuration since extra gain can not be utilized (allows to run at higher bias).
0
5
10
15
20
25
30
35
40
45
50
1000 1050 1100 1150 1200 1250 1300 1350
MCP bias (Volts)E
mit
tan
ce (
pi m
m m
rad
)
4500
9000
18000
22500
27000
31500
36000
40500
49500
54000
58500
63000
67500
Turn #
measurement: L. Short Bull
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 19
MCP test stand
• Built to measure eg gain depletion of used MCPs, and as a test bed for new systems (eg Tev IPM).
EGA On/Off #1
0
20
40
60
80
100
120
140
160
180
200
1 51 101 151 201 251
ADC Channel
No
. of
Co
un
ts
photo: A. Bross
measurement: B Dysert
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 20
Detector design
• Based on MI eIPM prototype– Flange-mounted
detector for quick installation
• Many modifications– Better screening– Different voltage
profile– Provisions for
calibration device
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 21
Beam EM screening
• Enclose anode board and signal cabling in Faraday cage!
• Wire mesh over MCP lets (most) electrons thru
• Avoid signal cable mismatch as far as possible
10kV
10kV
1kV
1kV
GND
GND
MI, Booster
Tev
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 22
Anode board
• ¼ mm strip pitch• 200 channels (128
instrumented)• Provision for on-board
LP filter/ back-termination (series resistor)
• Connected to feedtru by UHV compatible 50Ω flex-circuits
• High resolution area can be moved by swapping connectors
artwork: C. Lundberg
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 23
Beam based alignment
• Due to high strip aspect ratio (400:1), good alignment with beam is required.
• Motorized detector stands allows for beam-based elimination of any relative angle
• Translation is also possible, to scan active area on MCP
graph: K. O’Brien
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 24
Magnets
• Single corrector (two-bump) for simplicity.
• Electromagnets chosen.
• Can be turned off to verify effect on measurement and machine.
• Bought from outside manufacturer. design & photo: Scanditronix Magnet
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 25
Tracking – transverse displacement
• Ionization electrons simulated in B=0.2T, E=100kV/m.
• Transverse spread from electron momentum less than ¼mm pitch
• Small space-charge effect seen for protons at flat-top.
-0.4 -0.2 0 0.2 0.4Devaiation mm0
2
4
6
8
10
12
14
borP.
sneD.
protons at injection
-0.4 -0.2 0 0.2 0.4Devaiation mm0
2
4
6
8
borP.
sneD.
protons at flattop
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 26
Field quality
• Longitudinally, E-field is not perfect
• E×B component produces a small transverse drift velocity
• To first order, this generates a rotation of the beam “image”, which is removed by beam-based alignment
• Higher order terms distort the beam image, expect order ~30 nm rms effect on beam size.
-0.04 -0.02 0.02 0.04
-0.00015
-0.0001
-0.00005
0.00005
0.0001
0.00015
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 27
DAQ system
• CMS-QIE front end in tunnel.
• Serial data uplink on optical fiber
• Receiver and data buffer in upstairs PC
• Timing + clock + QIE settings supplied from PC thru cat-5E cable
Timing card(PCI)
Timingfanout
QIE cards(16x 8 ch)
Data Buffer(2*8 ch)
(PCI)
Host PC (LabView)
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 28
Timing card
• Produces the 15MHz (2/7 RF) FE clock
• Decodes and transmits beamsync clock (p & pbar) injection events
• Transmits QIE settings
• Separate version of card will decode TCLK/MDAT
design & photos: T. Fitzpatrick
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 29
396 ns (21 buckets)
p-pbar separation
RF
2/7
1/7
Timing scheme
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 30
Front end card
• 8 channels (CMS QIE) per board.
• Data is serialized by CERN GOL ASIC (rad hard) and sent thru fiber
• Timing fanout board cleans up and distributes clock and timing signals
tim
ing
fan
out
QIE
car
d
design & photos: K. Bowie
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 31
Data buffer card
• Handles 8 incoming optical channels
• Data stored in on-board RAM
• Read out thru 64 bit PCI bus
• Doubles as BTeV L1 data buffer prototype.
design & photo: R. Kwarciany
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 32
Differential pumping scheme
ion pump ion pump
ion pumpgauge
gauge
sector valvesectorvalve
orifice
vertipm
horzipm
Calibrated leakN2
ion pump ion pumpion pump
sectorvalve
ion pumpion pump
TSPTSP
shut-off valve
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 33
Simulated pressure profile
E0 IPM PUMPING
0.01
0.1
1
10
100
-180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180
Distance (inch)
P (
nT
orr
)
• Opening leak valve raises pressure by two orders of magnitude.
simulation: A. Chen
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 34
Controlled N2 leak tests at E4R
Red traces: IP and IG in leak chamberGreen, Blue and Cyan: IPs and IG in main chamber
6 hours
3 d
ecad
es
leak ontest setup: S. McCormick
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 35
Tunnel installation
Detector goes here!
11/11/2004 Tevatron Ionization Profile Monitor A. Jansson 36
Conclusions and outlook
• Tevatron IPM project well advanced• All infrastructure installed this
shutdown.• Detector unfortunately not installed
need a few days downtime (for vacuum bake).