The AEgIS Experiment Measuring the Gravitational Interaction of - - PowerPoint PPT Presentation

Andreas Knecht / CERN

• n behalf of the AEgIS collaboration

LEAP 2013, 10/6/2013

The AEgIS Experiment

Measuring the Gravitational Interaction of Antimatter

Andreas Knecht LEAP 2013, 10/6/2013

AEgIS Collaboration

2 University of Oslo and University

• f Bergen, Norway

CERN, Switzerland INFN Genova, Italy INFN Bologna, Italy Kirchhoff Institute of Physics, Heidelberg, Germany Max-Planck-Insitut für Kernphysik Heidelberg, Germany INFN, Università degli Studi and Politecnico Milano, Italy INFN Pavia-Brescia, Italy INR Moscow, Russia Université Claude Bernard, Lyon, France Czech Technical University, Prague, Czech Republic INFN Padova-Trento, Italy ETH Zurich, Switzerland Laboratoire Aimé Cotton, Orsay, France University College, London, United Kingdom Stefan Meyer Institut, Vienna, Austria University of Bern, Switzerland

Andreas Knecht LEAP 2013, 10/6/2013

Motivation

First direct test of the Weak Equivalence Principle involving antimatter

Direct tests so far only for matter systems Validity for antimatter inferred from heavily debated indirect arguments Theory could accommodate differences (e. g. through potential including gravivector and graviscalar)

3 Nieto and Goldman, Phys. Rep. 205, 221 (1991) Amole et al., Nat. Comm. 4:1785 (2013)

Andreas Knecht LEAP 2013, 10/6/2013

Motivation

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And quite generally: Experimental test of the gravitational interaction in a new sector - one for the textbooks (and for the public)!

Andreas Knecht LEAP 2013, 10/6/2013

AEgIS Experimental Goal

Primary goal:

Measurement of gravitational acceleration g for antihydrogen with 1% accuracy

Secondary goals:

Spectroscopy of antihydrogen Study of Rydberg atoms Positronium physics: formation, excitation, spectroscopy

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Produce ultra cold antiprotons Form positronium by interaction of positrons with a porous target (pulsed) Laser excite Ps to get Rydberg Ps (pulsed) Form Rydberg cold antihydrogen (pulsed) by Stark accelerate the antihydrogen with inhomogeneous electric fields → Pulsed production of a cold beam of antihydrogen Measure the gravitational acceleration in a classical moiré deflectometer

Andreas Knecht LEAP 2013, 10/6/2013

AEgIS Experimental Strategy

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Ps∗ + p → H

∗ + e−

Storry et al., PRL 93, 263401 (2004) Vliegen and Merkt, J. Phys. B:

• At. Mol. Opt. Phys. 39, L241 (2006)

Andreas Knecht LEAP 2013, 10/6/2013

Antihydrogen Formation

Positronium charge exchange technique:

Large cross-section, scales as n4 Narrow and defined final state distribution Antihydrogen production from antiprotons at rest

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Ps

laser excitation antiproton trap positronium converter

e+ Ps Ps* Ps* H* H*

H beam

H*

accelerating electric field

Ps∗ + p → H

∗ + e−

n(H) 10 20 30 40 50 60 70 80 prob 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

nPs = 35

Andreas Knecht LEAP 2013, 10/6/2013

Moiré Deflectometer

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grating 1 grating 2 position-sensitive detector L L atomic beam

Gr Gr units units

gt²

Classical deflectometer (shadow mask) Third grating replaced by position-sensitive detector

Andreas Knecht LEAP 2013, 10/6/2013

Moiré Deflectometer

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time (s) 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014 0.0016 0.0018 0.002 0.0022 Phase (rad) 0.5 1 1.5 2 2.5 3

Phase shift as a function of time (velocity of antihydrogen) gives gravitational acceleration: Δz ~ gt2

Andreas Knecht LEAP 2013, 10/6/2013

Experimental Apparatus

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p from AD _ Positron accumulator 5T magnet 1T magnet

Layout of the zone

Andreas Knecht LEAP 2013, 10/6/2013

Location

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Andreas Knecht LEAP 2013, 10/6/2013

Experimental Installation

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Zone early 2011 Zone late 2012

Andreas Knecht LEAP 2013, 10/6/2013

5T Catching Traps

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HV HV HV

1 2 3

Andreas Knecht LEAP 2013, 10/6/2013

1T Formation Traps

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Andreas Knecht LEAP 2013, 10/6/2013

Central Antihydrogen Detector

Scintillating fibre detector operating at 4K 800 channels readout by SiPM 200 MHz readout detecting hit pattern

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Andreas Knecht LEAP 2013, 10/6/2013

Positron System

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800 MBq 22Na source Solid neon moderator Positron trap Positron accumulator Buffer gas cooling Pulsed transfer line ~0.1T

Andreas Knecht LEAP 2013, 10/6/2013

Positron System

Ongoing work to increase rates and efficiencies

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200 400 600 800 20 40 60 80 100 120

Time (s)

Lifetime = 29+/-2 s fill time = 120 s 7-8 10

6 e +

3 10

6 e +

Lifetime = 12+/-1 s fill time = 38 s 5 10

6 e +

6 10

6 e +

counts (a.u.) Pulse number

Lifetime = 25+/-2 s fill time = 100 s

e+

Dump intensity 7-8 106 e+

5-6 x 104 e+ from trap M o d e r a t i o n - Tr a n s p o r t efficiency ~ 2.5 10-2 Spot dimension 4-5 mm Spot dimension 1-2 mm Trapping-dumping efficiency ~ 0.14

e+

Dump intensity 7-8 106 Lifetime ~30 s Fill time ~120 s Transport efficiency ~80-90 %

Andreas Knecht LEAP 2013, 10/6/2013

Commissioning Results

Trapping, cooling

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Trapping voltage [kV] 1 2 3 4 5 6 7 8 9 ]

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Antiprotons caught [ x10 0.2 0.4 0.6 0.8 1 1.2 1.4

Antiproton catching vs applied high voltage

Antiproton cooling time [s] 5 10 15 20 25 30 35 40 Cold / hot antiproton fraction 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Cold and hot antiproton fractions vs. electron cooling time

Andreas Knecht LEAP 2013, 10/6/2013

Commissioning Results

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Lifetime ~500 s

Storing

sec 50 100 150 200 250 300 Trapped antiprotons 20 40 60 80 100 120 140

3

10 ×

Hot antiprotons storage time 9 KV

Cold antiproton storage

Andreas Knecht LEAP 2013, 10/6/2013

Commissioning Results

Manipulations

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Andreas Knecht LEAP 2013, 10/6/2013

Commissioning Results

Positron transfers through transfer line and 5T into 1T magnet

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Extraction pulse from accumulator Scintillator pulses from positron annihilation in 1T

Andreas Knecht LEAP 2013, 10/6/2013

Detector Tests

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Parasitic tests: Silicon detectors (strip, pixel) MCP Emulsions Explore different candidate technologies for the (downstream) antihydrogen detector

See poster by O. Karamyshev

Andreas Knecht LEAP 2013, 10/6/2013

Silicon Detectors

3D pixel sensor designed for the ATLAS upgrade Also tested: strip sensor, Mimotera

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p _

Probability

0.02 0.04 0.06 0.08 0.1 0.12 0.14

FTF Chips Data

[MeV]

tot

E 5 10 15 20 25 30

DATA

/N

SIM

N 1 2

X 20 40 60 80 100 Y 20 40 60 80 100 1000 2000 3000 4000 5000 6000 7000

Andreas Knecht LEAP 2013, 10/6/2013

Mimotera Detector

112 x 112 silicon pixel detector, 153 μm x 153 μm, 15 μm active depth Detailed comparison of data vs simulation Test of Monte Carlo treatment of antiproton annihilations on bare silicon

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Publication forthcoming!

Preliminary

Andreas Knecht LEAP 2013, 10/6/2013

Emulsions

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Exposure of emulsion Development in dark room Scanning on automated microscopes Offline track and vertex finding algorithms 1 μm vertex resolution

See talk by J. Storey Friday @ 9:55 am

Glass%base% 1%mm%

Emulsion) layer)) (50)micron))

Focus& an#proton(

Base (glass or plastic) (several 100 μm)

Andreas Knecht LEAP 2013, 10/6/2013

First Test of Moiré Deflectometer

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emulsion

d ref

~100 keV antiprotons 7 hour exposure Bare emulsion behind deflectometer

Andreas Knecht LEAP 2013, 10/6/2013

First Test of Moiré Deflectometer

Antiproton fringes observed Alignment of gratings using light and single grating Promising results!

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Publication forthcoming!

Rotation (rad)

• 0.03
• 0.02
• 0.01

0.01 0.02 0.03 Period 39 39.2 39.4 39.6 39.8 40 40.2 40.4 40.6 40.8 20 40 60 80 100

Cross-correlation method

Preliminary

Andreas Knecht LEAP 2013, 10/6/2013

Conclusions and Outlook

Installation of apparatus largely completed and commissioned Parasitic measurements essential in converging to an optimal deflectometer/detector layout Next steps:

Install proton source, hydrogen detector Commission Rydberg positronium formation Work on hydrogen formation/characterization Goal: Be ready for antihydrogen beam formation in summer 2014!

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Andreas Knecht LEAP 2013, 10/6/2013

Backup

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Positronium target - parameters

Ultracold antiprotons

Antiprotons in the trap cannot be directly cooled to 100 mK

Cool antiprotons by collisions with a partner particle stored in the same trap that can be cooled

e- antiproton

L C

electrons

Resistive cooling with a resonant tuned circuit + radiation cooling Laser cooling of La_ Ultimate temperature: 240 nK

Negative ions: La-

• A demonstration of laser cooling of negative ions is needed
• Experiment in progress at MPI (members of AEGIS)

antiprotons

Embedded electron cooling, adiabatic cooling, evaporative cooling, ...

Harmonic Generator n=1 → n=3 205 nm Transition saturation energy: ~2 µJ n=3 → Rydberg 1650-1700 nm Transition saturation energy: ~0.2 mJ Nd:YAG 1064 nm 650 mJ, 5 ns

4th 2nd

1st

OPG

OPG + OPA

SUM OPA

894 nm 1650-1700 nm 266 nm 532 nm 1064 nm

Laser source and harmonic generator: Tender will start within December 2010 (?) Expected arrive in March - April 2011 Goal of the apparatus: About 10 times the saturation energy

Rydberg excitation via a simultaneous two step incoherent process: 1 → 3 → Rydberg (wavelengths: 205 nm and 1650 - 1700 nm) Main effects of level broadening:

1 → 3: Doppler effect (~0.04 nm) due to velocity distribution of Ps 3 → Rydberg: Motional Stark effect (makes a quasi-continuum from n=17, each level is broadened to many nm) due to Ps movement in a strong B field

Lasers

components delivered in April 2011 (pumping laser delivered in autumn 2011)

Laser system: power tests

required level = 2μJ required level = 200μJ

Moiré deflectometer: first tests

Faraday cup (detects integral

• f incoming

atom beam) small distance for higher contrast small prototype grating structures loading flange last grating is used to scan fringe pattern

 v1

Moiré deflectometer: 6” (full size) grating prototype