a2 collaboration meeting feb 2011 – peter-bernd otte

A2 collaboration meeting Feb 2011, Peter-Bernd Otte

A2 Collaboration Meeting Feb 2011 – Peter-Bernd Otte

Status New Trigger & Beam Polarimetry

e1

→e2

→

polarisedfoil

e1′→


Brevity is the soul of wit

FPGA

~3 cm

~ meters

• = semiconductor chip

• FPGA = • many electronics modules (like OR, MLU)• cables

• no CPU!

“VUPROM” from GSIwith “Virtex 4” from XILINX


Part A: New Experiment Trigger

Setup of New Trigger

CB

PID

1st stage VUPROM

1st stage VUPROM

1st stage VUPROM

1st stage VUPROM

level converter

& cable

masterVUPROMcables

Exp. trigger

70nsComputation time:460ns for Multiplicity (LT = 98.7%)20ns for Coplanarity (LT = 100%)

Cellular Cluster Counter



• cellular logic• Steps

1. gather hit pattern (330ns)

2. Shrink clusters (60ns)(using set of rules)until no more changes

3. Count number of cells (20ns)= number of clusters

4. If desired cluster count trigger!

Multiplicity cluster algorithm

crystal scheme of CB



Algorithm universality

+ 180° rotated together 6x

Not all rules are valid for all crystals at all times.

1 2

3

1

5

2

3

14

2

3

14

5

2

3

1

510

6

2

3

+120° & +240° rotated

cure wholes

Shrink

CB TAPS

together 6x



Future

New CB trigger• works

since several months in parallel to the existing one

• awaits integration into L1/L2

• Remaining:purity and efficiency?

More sophisticated triggers possible with:

CB, PID, TAPS, MWPC in combination for L1/L2


Part B: Beam polarimetry

e- beam polarimetry

Tagger

e-

radiator

e

Measure degree of e- beam polarisationusing Moeller polarimeter

Good news:No big energy shift anymore! • now correct calibration for “new Tagger”• only ~1ch due to optics



e- beam polarimetry works, but: mark “C”26

/11/

2010

12:

00

27/1

1/20

10 1

2:00

28/1

1/20

10 1

2:00

29/1

1/20

10 1

2:00

30/1

1/20

10 1

2:00

01/1

2/20

10 1

2:00

02/1

2/20

10 1

2:00

03/1

2/20

10 1

2:00

04/1

2/20

10 1

2:00

05/1

2/20

10 1

2:00

06/1

2/20

10 1

2:00

40

50

60

70

80

90

100

long

. deg

ree

of p

olar

isati

on i

n %



• 100 histograms/FPGA, here 2 samples

• Reason: detector. • Proof: measured with two different electronics

shaky measurements

time diff. /ch time diff. /ch

low humming Strong humming

=



• I5 and P7 channels of tagger:

• Humming = leads to biggest uncertainty in Moeller

Humming in Tagger (no noise!)



• Why not constant?

e- source flux normalisation

Tagger section A B C D E F G H I J K L M N O P

e

e

N

N

~3% in pol. degree



• 8th Feb work on beam dump dump position changed (?) 0.4% tagger magnet field change

0 to 2 channels shift in Tagger change in Moeller electronics and analysis needed

• Polarisation bit beam polarisation – possible to be obtained– MAMI energy dependent

Beam polarimetry



• 5 VUPROMs in Tagger rack =1. Moeller electronics2. planned as monitor for linear photons polarisation:

indep. Tagger scalers with pair spectrometer as gate Patrik's talk

3. selection of single tagger channels for tests

Electronics in Tagger area

old


Part C: Problems

Problem in existing exp. trigger

Start of TDC at „CB Energy Sum“Start of TDC at „CB Energy Sum“

Stop of TDC at „TCS Trig“ / Exp. Trigger

Stop of TDC at „TCS Trig“ / Exp. Trigger

1% unclear

300ns


A2 Collaboration Meeting Feb 2011 – Peter-Bernd Otte

Status elog


• http://elog.office.a2.kph (user: a2online)

• elog from PSI (Stefan Ritt), open source, widely used und known– Many people in our group can assist– No text losses and locks anymore– Data from existing elog has been

imported

• Data reliability– uses infrastructure from KPH

computing group– virtual computer with RAID 5 (+ remote

hot mirror) and snapshots paperless future

• Everybody or group can have his/their own logbook

elog

http://elog.office.a2.kph/


Part C: Problems

The all new keyboard

New keyboard for all German PhD students. Makes life easier…

K.T. zu Guttenberg,Minister of Defence

“Wrote” >20% of his PhD with

Thanks for listening!


Appendix



• Trigger = 2 hits in plane with incoming g (only azimuthal) |f1 – f2| = 180 deg

• divide CB into 48 azimuthal bins • “hardwired” trigger with ANDs and ORs

• immediate trigger result Livetime = ~100%• rate: 580Hz

(while M1+ = 16k, M2+ = 3.6k)

Coplanarity trigger

direction of beam

24xsublogic

OR

AND

Simulation by Cristina Collicott (D. Hornidge)



• Measured: Azimuth angle difference between hit channels in CB

Coplanarity trigger

Number of clusters (M) determined by FPGA logic



Setup of New Trigger: Multiplicity Trigger

CB(NaI)

PID

1st stage VUPROM

1st stage VUPROM

1st stage VUPROM

1st stage VUPROM

level converter

& cable

masterVUPROMcables

signal to all: Send full hit pattern

Exp. trigger

70ns 20ns 15ns

310ns 100-120ns+

Detailed hit pattern needed full readout!


• Rates:

• livetime: 98.7%

• Next step: determine purity and efficiency

• Same trigger algorithms can be extended to cover also TAPS

Multiplicity Trigger: Rates

New Trigger (CB only) Existing (CB and TAPS)

M1+ 20k 40k

M2+ 4.5k 6.0k

M3+ 1.6k 2.2k


Teil 2: Trigger-Logiken

Bonn (2000) Mainz (2010)

Geschwindigkeit (nur Berechnung)

bis zu 10µs/Cluster 120ns insg.

Logik Zellularer Aufbau aber sequentielle Bearbeitung

Echt zellulare Logik

Im Vergleich


Part B: Moeller Polarimeter

• Use Moeller scattering– measure 2 coincident electrons

DAQ necessary

– Count asymmetry

beam polarity

Introduction electron beam polarimetry

BeamEEE 21

NN

NNA

e1

→e2

→

polarisedfoil

e1′→

e2′→

use Tagger


Detectors of Tagger


• Moeller radiator• Tagger• 4x VUPROMs

Moeller Polarimeter Setup

e1

→

e2

→e1 ′

→

e2 ′

→

1 352

VUPROM 1

VUPROM 2

VUPROM 3

VUPROM 4

AB

EF

GH

IJ OP

QR

ST

UV

Complete DAQ on a chip.Per FPGA:

24x TDC (resolution 50ps) & 50 histograms



• same e- energy and entry anglebutdifferent angles signs

Simulate Moeller electrons (Tagger optics)

0 50 100 150 200 250 300 350

-10

-5

0

5

10

15

pos. angle

neg. angle

Taggerchan.

ener

gy s

hift

in M

eV

(450 MeV beam energy)



• Sum of energy shift

Simulate Moeller electrons (Tagger optics)

0 50 100 150 200 250 300 350 400 450

-8

-6

-4

-2

0

2

4

6

8

10

a2 collaboration meeting feb 2011 – peter-bernd otte

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