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 …


Talk outline

• Motivation for IPMs in Tevatron• Special challenges in Tevatron• Design of Tevatron IPMs• Tests• Pictures from “down under”.


Motivation

• Directly measure injection matching and emittance growth at injection

• Continuously measure emittance eg on ramp


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.


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)


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!


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


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.


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


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


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)


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


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


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


Rad level measurements

• Reading 125 mrad/h during normal running at ~4.5 feet

• 18 years to 20 krad!


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


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


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


Detector design

• Based on MI eIPM prototype– Flange-mounted

detector for quick installation

• Many modifications– Better screening– Different voltage

profile– Provisions for

calibration device


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


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


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


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


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


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


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)


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


396 ns (21 buckets)

p-pbar separation

RF

2/7

1/7

Timing scheme


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


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


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


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


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


Tunnel installation

Detector goes here!


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).

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TEVATRON IONIZATION PROFILE MONITOR Andreas Jansson Fermilab.

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