High rate and photon test beams with the MuPix at MAMI
Alexey Tyukin
Mainz Institute for Nuclear Physics
26.01.2017 BTTB Barcelona
Outline
The MAMI accelerator MuPix Chip
Photon test beam results
High electron rate results with the MuPix telescope
The Mainz Microton (MAMI)
Electron accelerator up to 1.6 GeV
Beam current up to 100 µA at 2.45 GHz continuous wave
Halls for experiments with electrons, high energy photons and x rays
2
Accelerator Stages
3-stage microtron cascade Racetrack microtrons Output 14, 180, 855 MeV
4-th stage: double-sided microtron 1.6 GeV final energy
[1]
The MAMI beam
High quality beam suitable for parity violation experiments Typical beam size < 1 mm
Energy stability to 2·10−5
Beam can have polarisation of 85%
Emittance at 855 MeV of 40.8 mm·mrad (hor) and 3.8 mm·mrad (vert)
[2]
Figure:phase space (horizontal and vertical) of the beam for different polarisations at 0.1 MeV. Boundry shows 1σarea, emittance scales with∝√
E
4
MAMI operation time
0 1000 2000 3000 4000 5000 6000 7000 8000
00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16
Year
Operating hours [h]
setup, tuning, development unpolarized polarized
MAMI has a high duty factor of up to 70%
Proposals for test beam time or experiments with existing detectors welcome!
MESA: a new accelerator near MAMI
Mainz Energy-recovering Superconducting Accelerator planned for 2020
Figure:A new accelerator is being built adjacent to MAMI
An independent newe−-accelerator up to 155 MeV
Highly stable beam up to 150 µA for future precision experiments Two experiments being planned: P2andMAGIX
P2 Experiment requires electron tracker operating in high photon background
6
The MuPix Chip
The MuPix chip is going to be used in the Mu3e, P2 and PANDA experiment
[5]
Originally designed for theMu3eexperiment
Fast, thin high voltage monolithic active pixel sensor (HV-MAPS) pixelsize 80x103 µm, time resolution 11 ns
Currently a 3x3 mm version with 1280 pixels available
For experiments large area trackers out of MuPix chips planned
Beam test locations
Direct irradition with the MAMI beam behind RTM3 Photon test beam location behind A2 Tagger
Additionally there is space behind the A2 Tagger suitable for tests with the deflected electrons
8
High energy photon beamtime - A2 Setup
E0= 450MeV
Vacuum Window (Mylar) Permanent
Magnet MuPix Sensor Dipole
[3]
Efficiency measurement at photon energies from 22.3 to 419 MeV Using the photon beam of A2 to irradiate a MuPix chip
100 pA of 450 MeV electrons hitting Fe/Cu foil and produce bremsstrahlung photons
Additional measurement of tagging efficiency with a lead glass detector
High energy photon beamtime - Time coincidende and hitmap
[3] Column index
0 5 10 15 20 25 30
Row index
0 5 10 15 20 25 30 35
0 0.05 0.1 0.15 0.2 0.25 0.3
106
×
[3]
Coicidence between the tagger and the chip Photon spot visible in the hitmap
True photon efficiency can be obtained by correcting for tagging efficiency Correction for the sensor size required
10
High energy photon beamtime - Simulation
Photon Energy / MeV
50 100 150 200 250 300 350 400
detη
0 0.5 1 1.5 2 2.5
−3
×10
Detector Response to Photons Photoelectric Effect outside Sensor Photoelectric Effect inside Sensor Compton Scattering outside Sensor Compton Scattering inside Sensor Pair Creation outside Sensor Pair Creation inside Sensor
[3]
Geant4 simulation: main signal contribution from pair production Air in front of the chip producede+/e−pairs hitting the chip Efficiencyηdet prediction is between 0.25·10−3 and 1.85·10−3
High energy photon beamtime - Result
50 100 150 200 250 300 350 400
Photon Energy / MeV 0.5
1.0 1.5
ηdet2.01e-3
MC prediction Corrected Data with stat. error Systematic error
[3]
Measured efficiencies agree well with prediction More studies at lower photon energies needed
A magnet in front of the chip could solve the problem of pair production in air
12
High electron rate beamtimes
Figure:Beam hitting 4 chips successively
MAMI beam at 855 MeV hitting a telescope of 4 MuPix chips Beam intensity can be chosen arbitrarily low - or full intensity of 6·1014e−/s
Beam profile can be seen in all four chips, if they are aligned well
High electron rate beamtimes - Pixelmap
Pixel rates at 2.8 MHz total rate:
pixelmap_on_X2_
Entries 1.788995e+07
Mean 18.13
RMS 4.083
0 5 10 15 20 25 30
0 200 400 600 800 1000 1200 1400 1600 1800 103
×
pixelmap_on_X2_
Entries 1.788995e+07
Mean 18.13
RMS 4.083
pixel map projected on X2_
pixelmap_on_Y2_
Entries 1.788995e+07
Mean 26.29
RMS 5.511
0 5 10 15 20 25 30 35
0 200 400 600 800 1000 1200 1400 103
×
pixelmap_on_Y2_
Entries 1.788995e+07
Mean 26.29
RMS 5.511
pixel map projected on Y2_
Beamspot rms after an aluminum window and 1 m of air: 0.42 x 0.44 mm 14
High electron rate beamtimes - Track residuals
Run number
80 100 120 140 160 180
Residuals x mean [um]
−2
−1 0 1 2
Run number
80 100 120 140 160 180
RMS of residuals x mean [um]
18 20 22 24 26
We can reconstruct tracks when the electrons hit all four chips Track efficiency at the chosen cuts was≈45%
Residuals mean changes slighly over time
High electron rate beamtimes - Efficiency map
The efficiency is mostly constant over the whole chip at low rates At high rates we start getting inefficiencies in the highest irradiated pixels Deadtimes after each hit of approximatly 600 ns
16
High electron rate beamtimes
Rate [1/s]
0 500 1000 1500 2000 2500
103
×
Efficiency
0.99 0.991 0.992 0.993 0.994 0.995 0.996 0.997 0.998 0.999 1
/ ndf
χ2 14.63 / 63
p0 0.9975 ± 0.0001364 p1 −1.204e−09 ± 8.574e−11
/ ndf
χ2 14.63 / 63
p0 0.9975 ± 0.0001364 p1 −1.204e−09 ± 8.574e−11 Efficiency vs rate
Efficiency dependence of the beam rate up to 2.5 MHz
Slope of 0.12%per MHz shows high stability at rates higher than experiment requirements
Summary
MAMI is a suitable facility for beam tests with high electron rates and high energy photons
The narrow high quality electron beam can be extracted at 855 MeV Tagged photon beam up to 1.6 GeV
Photon efficiency upper limit of 0.25·10−3 and 1.85·10−3 between 22.3 to 419 MeV measured with the MuPix chip
MuPix chip efficiency loss of 0.12%per MHz of 855 MeV electrons
Figure:The Mainz Cathedral
18
Sources
1 Untersuchungen zur Strahldynanik am Harmonischen Doppelseitigen Mikrotron von MAMI-C, Dissertation, Marco Dehn, 2013
2 Operation of the MAMI accelerator with a Wien filter based spin rotation system, V. Tioukine, K. Aulenbacher, Nucl. Inst.a.M. A 568, 2006 3 HV-MAPS Photon Beam Test, Marco Zimmermann, July 11 2016 4 Experimental Study of nucleon resonance contributions to
η-photoproduction on the neutron, Dissertation, Dominik Werthmueller, 2014
5 A novel monolithic pixelated particle detector implemented in high-voltage CMOS technology, Ican Peric, Nucl. Inst.a.M. A 582, 2007
One problem: Beam spots
Run number
340 360 380 400 420
Rate [1/s]
3000 3500 4000 4500 5000
103
×
Rate plane 4 per Run
Operating the beam at a constant beam current, sometimes a sudden rise in the rate of some chips could be observed.
20
Beam spots
0 5 10 15 20 25 30
0 5 10 15 20 25 30 35
pixelrate_map_4_
Entries 1.779567e+07 Mean x 16.59 Mean y 20.96
RMS x 4.847
RMS y 6.56
0 2000 4000 6000 8000 10000 12000 14000 16000 pixelrate_map_4_
Entries 1.779567e+07 Mean x 16.59 Mean y 20.96
RMS x 4.847
RMS y 6.56
pixelrate map for sensor 4_
0 5 10 15 20 25 30
0 5 10 15 20 25 30 35
pixelrate_map_4_
Entries 1.687173e+07 Mean x 16.41 Mean y 21.17
RMS x 1.242
RMS y 1.809
0 20 40 60 80 100 103
× pixelrate_map_4_
Entries 1.687173e+07 Mean x 16.41 Mean y 21.17
RMS x 1.242
RMS y 1.809
pixelrate map for sensor 4_
After switching the beam off, a beamspot was visible in the hitmap. A charge-up effect lead generation of hits without any particles passing through. This would mean severe noise increase in a real experiment.
Beam spots
rateOverRunPlane1
Entries 124
Mean 55.57
RMS 35.75
Prob 1.634e−20 p0 7.605e+04 ± 3.396e+03 p1 7.438e+04 ± 3.317e+03 p2 −0.01531 ± 0.00058 p3 −83.59 ± 17.41
time [sec]
0 20 40 60 80 100 120
Hitrate [1/s]
0 20 40 60 80 100 120 140
103
×
rateOverRunPlane1
Entries 124
Mean 55.57
RMS 35.75
Prob 1.634e−20 p0 7.605e+04 ± 3.396e+03 p1 7.438e+04 ± 3.317e+03 p2 −0.01531 ± 0.00058 p3 −83.59 ± 17.41
rate over run on plane 1
The beamspot decays with different speeds depening on its intensity.
22
Electron scattering at A1
Precision electron scattering experiments with 3 rotatable spectrometers VDCs with momentum resolution to 10−4
Electron energy exceeds the production threshold for several Mesons and Hyperons
Photon scattering at A2
[4]
Figure:The Crystal-Ball is a 4πcalorimeter around the main target[4]
Photons between 22-1500 MeV are produced by bremsstrahlung on the radiator
A dipole deflects the beam electrons and allows momentum measurement in the focal plane detector
Photons go through a collimator to the main target
24
