A2 collaboration meeting Oct 2010, Peter-Bernd Otte

A2 Collaboration Meeting Oct 2010 – Peter-Bernd Otte

New Trigger&

Moeller Polarimeter

e1

→ e2

→

polarisedfoil

e1′→

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Brevity is the soul of wit

FPGA

~3 cm

~ meters

• = semiconductor chip

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

• no CPU!

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part A: New Experiment Trigger

Setup of New Trigger

CB(NaI)

PID

1st stage VUPROM

1st stage VUPROM

1st stage VUPROM

1st stage VUPROM

level converter

& cable

masterVUPROMcables Exp.

trigger

70ns 20ns 15ns

“VUPROM” from GSIwith “Virtex 4” from XILINX

discriminatoroutput

clustering &logic

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part A: New Experiment Trigger

• 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)

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part A: New Experiment Trigger

• Measured: Azimuth angle difference between hit channels in CB

Coplanarity trigger

Number of clusters (M) determined by FPGA logic

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part A: New Experiment Trigger

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!

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part A: New Experiment Trigger

• 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

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

• 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

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part B: Moeller Polarimeter

• Use Moeller scattering– measure 2 coincident electrons

DAQ necessary

– Count asymmetry

beam polarity

Introduction electron beam polarimetry

BeamEEE 21

NNNNA

e1

→ e2

→

polarisedfoil

e1′→

e2′→

use Tagger

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Detectors of Tagger

Part B: Moeller Polarimeter

• Moeller radiator• Tagger• 4x VUPROMs

Moeller Polarimeter Setup

e1

→e

2

→

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

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part B: Moeller Polarimeter

• Moeller electronics and DAQ work!• Raw data:

Electronics and DAQ

1 352

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part B: Moeller Polarimeter

• Count asymmetries okay!• Abs. value not okay, due to problematic energy calibration of Tagger

Results: MAMI angle scan

450MeV beam energy 1557MeV beam energy

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part B: Moeller Polarimeter

• Moeller electronics and DAQ work!• Raw data:

Electronics and DAQ

1 352

Expected Moeller pairs.

But energy shift measured: 4 to 12 channels

Why important?

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part B: Moeller Polarimeter

• Why? – e- entry angle Moeller >> bremsstrahlung

Tagger calibration only valid for small angles

• Result: Mapping of electron energy and angle dependent. shift in measured energy

Origin of measured energy shift (Tagger optics)

e-

pos. angle

neg. angle

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part B: Moeller Polarimeter

• 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.en

ergy

shift

in M

eV

(450 MeV beam energy)

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part B: Moeller Polarimeter

• Sum of energy shift

Simulate Moeller electrons (Tagger optics)

0 50 100 150 200 250 300 350 400 450

-10

-5

0

5

10

15

20

measurement

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

• New coplanarity & multiplicity trigger: works!– Remaining: purity, efficiency? next weeks

• Moeller polarimeter– count rate asymmetries: okay– abs. polarisation: unknown ideas welcome has this been discovered in the past?

Summary

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part B: Moeller Polarimeter

• Ingredients: – simulated field map (MAMI B or MAMI C?)– map electrons (0..450MeV) onto tagger ladder/beam dump

Setup of Simulation (Tagger optics)

Beam dump

e- gun

tagger ladder

Use own calibration for calculationsIan Antonow

1 19 37 55 73 91 1091271451631811992172352532712893073253430.96

0.97

0.98

0.99

1

1.01

1.02

1.03

1.04

E simul

ation

/ E ca

libra

tion

Tagger channel

A2 collaboration meeting Oct 2010, Peter-Bernd Otte

Part B: Moeller Polarimeter

• scattering angle:

• 94-92% loss of Moeller e- due to small Tagger pol shoe gap

Simulate Moeller electrons

Moeller e-180MeV

1508MeV

bremsstrahlung e-

Moeller e-pole shoes

angl

e in

lab

fram

e

Simulation only in accelerator plane