Strategies for the detection - PowerPoint Presentation

Slide1

Strategies for the detection of n=3 and Rydberg Positronium levels in the experiment

Zeudi MazzottaSupervisor: Fabrizio Castelli

1

AEGIS

AEGISSlide2

OUTLINE17/11/2014 First Year Workshop2The AEgIS experimentThe role

of the Positronium in the AEgIS

experimentPositronium

Laser excitation and

its detectionSlide3

The physics behind the AEgIS experiment 17/11/2014 First Year Workshop

3Slide4

17/11/2014 First Year Workshop4All matter bodies at the same spacetime point in a given matter gravitational field will undergo the same acceleration

The

weak equivalence

principle

(WEP)The physics behind the AEgIS experiment

All antimatter bodies at the same

spacetime point in a given antimatter gravitational field will undergo the same

accelerationSlide5

17/11/2014 First Year Workshop5All matter bodies at the same spacetime point in a given matter gravitational field will undergo the same acceleration

The

weak

equivalence principle (WEP)

The physics behind the AEgIS experiment

All antimatter bodies at the same spacetime

point in a given

antimatter

gravitational

field will undergo the same

acceleration

Will all

antimatter

bodies

at the same

spacetime

point in a given

matter

gravitational

field

undergo

the same

acceleration?Slide6

The AEgIS experiment 17/11/2014 First Year Workshop6Slide7

The main goal of AEgIS17/11/2014 First Year Workshop7Measurement

of the gravitational acceleration

of the

antimatter into

the Earth gravitational field

 The

AEgIS experiment

Neutral

antimatter

:

A

ntihydrogen

?Slide8

Antihydrogen production17/11/2014 First Year Workshop8The AEgIS

experiment

AEgIS

strategy

PROMISING

TECHNIQUE

Control of the

antihydrogen

quantum state

Cold

antihydrogen

atoms

(

v

antihydrogen

~

v

antiproton

)

Advantages in the cross section (see later

)

Usual

strategy

:

ATRAP,APLHA and ASACUSA

experiments

The

second

seems

to be the

dominant

process

(

highly

exicited

antihydrogen

)

A

ntihydrogen

atoms

warmer

than

trapped

antiprotons

(

Hbar

production

when

v

antiproton

~

v

positron

)

Low cross section

Antiprotons

and

positrons

Recombinations

and

Charge

exchange

with

P

ositroniumSlide9

17/11/2014 First Year Workshop9The Positronium atomorto-PsTriplet stateMean life 142ns

3g annihilation

g

g

g

g

g

para-Ps

Singlet

state

Mean

life

0,125ns

2

g

annihilation

g

Energies

= 511keV

g

Energies

< 511keV

Ps n-

level

energy

:

The

AEgIS

experimentSlide10

AEgIS in short17/11/2014 First Year Workshop10The AEgIS experiment

e+ beam

Antiprotons

from CERN AD(

Antiproton Decelerator)

p-

p

-

e

+Slide11

AEgIS in short17/11/2014 First Year Workshop11The AEgIS experiment

e

+

pulse

dumping and

acceleration

5

Tesla

magnet

antiprotons

cooling

(~1K) and

trapping

p

-

e

+

e+ accumulatorSlide12

AEgIS in short17/11/2014 First Year Workshop12The AEgIS experiment

1 Tesla

magnet

e+ pulse

implantation and Positronium formation

Trapped&cooled

antiprotonsSlide13

AEgIS in short17/11/2014 First Year Workshop13The AEgIS experiment

Ps

and

p-

overlap region:

Charge exchange reaction

takes place!

1 Tesla

magnetSlide14

AEgIS in short17/11/2014 First Year Workshop14The AEgIS experiment

1 Tesla

magnet

Antihydrogen

accelerated

beamSlide15

AEgIS in short17/11/2014 First Year Workshop15The AEgIS experiment

Moirè

deflectometer

 Slide16

The role of the Positronium in the AEgIS experiment17/11/2014 First Year Workshop

The role of the Positronium

in the AEgIS experimentSlide17

Positron

pulse

17/11/2014 First Year Workshop

17

The

role

of the

Positronium

in the

AEgIS

experiment

The

Positronium

creation

A

bunched

positron

beam

is

sent

toward

a

porous

«target»

able

to

convert

positrons

into

Positronium

.

Silica

or

aerogel

target

Positronium

cloud

Positronium

is

created

in the

material

bulk

A

fraction

of the Ps

exiting

the target

is

thermalized

into

the target

pores

Pores

diameter

~

10nmSlide18

17/11/2014 First Year Workshop18The role of the Positronium in the AEgIS experimentThe role of the Positronium in the AEgIS

experiment

Ps

is

needed to create

Antihydrogen in theCharge exchange

reactionThe

cross

section

of

this

reaction

increases

with the Ps

principal

quantum

number

:

Required

Ps

excitation

to

Rydberg

levels

(n=15…24

) !!!

distance

Ps areaSlide19

Positronium laser excitation and its detection17/11/2014 First Year Workshop19Slide20

AEgIS Ps Rydberg laserexcitation strategy17/11/2014 First Year Workshop20

n

=1

n=3

Continuum

High n

6,05eV

205nm

0,75eV

~1670nm

Positronium

Laser

excitation

and

its

detection

We

have

to test

if

the laser

excitation

works

!

Use of

an

external

test

chamber

,

called

BREADBOXSlide21

n=3 excitation detection strategiesChanges in the g-rays time distributionDetection

of 1312nm photons

(spontaneously emitted

in the n=3->n=2 de-excitation

branch)

Ps laser ionization and charges

collection17/11/2014 First Year Workshop

21

Positronium

Laser

excitation

and

its

detectionSlide22

1.Detecting Ps n=3laser excitationBy measuring changes in the g-rays time distribution

Positronium Laser excitation

and its detection

17/11/2014 First Year WorkshopSlide23

1. Detection of Ps annihilations into gamma rays time distribution17/11/2014 First Year Workshop23

para-Ps

orto-Ps

Only

0.124ns

to

decay into

2

g

-rays

Singlet-triplet

mixing

due to the

presence

of a

weak

magnetic

field

(~200G)

that

mixes

levels

with the

same

m

Observation

of

enhanced

2

g

rays

annihilation

rate

at

the time of laser on

Positronium

Laser

excitation

and

its

detection

UV laser

Triplet

142ns

to

decay

into

3

g

-rays

Spontaneous

emission

:

about

10ns

g

g

Singlet

n

=1

n=3Slide24

17/11/2014 First Year Workshop24Positronium Laser excitation and its detectionFirst simulation on Ps formation, excitation and TOF detection

3D

Histogram

:

BreadBox

walls picture

in the

simulation

Detectors

Target

My Montecarlo simulation

c++ & ROOTSlide25

My Montecarlo simulationc++ & ROOT17/11/2014 First Year Workshop25Positronium Laser excitation and its detection

3D

Histogram

:

Ps

annihilation

points

First

simulation

on Ps

formation

,

excitation

and TOF

detection

In

each

annihilation

point

we

have

g

-

rays

generation! Slide26

17/11/2014 First Year Workshop26Positronium Laser excitation and its detection

3D

Histogram

:

g-rays

intersections with the detectors

First

simulation

on Ps

formation

,

excitation

and TOF

detection

In

each

annihilation

point

we

have

g

-

rays

generation!

My

M

ontecarlo

simulation

c++

& ROOTSlide27

17/11/2014 First Year Workshop27Positronium Laser excitation and its detectionFirst simulation on Ps formation, excitation and TOF detection

Elements

taken into account

Laser

physicsDoppler effect

(Due to Ps Velocities)Excitation

efficiency Ps Velocities

and position

Chamber

geometry

Positronium

physics

Mean

lives

Maxwell-

Boltzmann

velocities

distributions

Decaying

times

Annihilation

behaviours

Gamma-

rays

energies

generation

Detectors

physics

Efficiency

Time

resolution

Energy

resolution

My

M

ontecarlo

simulation

c++

& ROOTSlide28

1. Detection of Ps annihilations into gamma rays time17/11/2014 First Year Workshop28

Positronium Laser excitation

and its detection

Mean of 10

signals of

Ps atoms Slide29

17/11/2014 First Year Workshop291.

Detection of Ps annihilations

into gamma rays time

Mean

of 10

signals of

Ps atoms

Increase

of the «

fast

decaying

»

population

and relative

decrease

of the «

slower

»

counterpart

Positronium

Laser

excitation

and

its

detectionSlide30

2.Detecting Ps n = 3laser excitationBy measuring the 3->2 spontaneous emission

radiation

17/11/2014 First Year WorkshopPositronium

Laser excitation and

its detectionSlide31

2. Detection of 1312nm photons17/11/2014 First Year Workshop31

n

=1

n=3

n=2

6,05eV205nm

1312nmradiation

Excitation

De-

excitation

The goal of

this

strategy

is

to

detect

the

radiation

emitted

from

this

transition

Positronium

Laser

excitation

and

its

detection

8

5%

15%Slide32

2. Detection of 1312nm photons17/11/2014 First Year Workshop32

InGaAsdetector

We

chose

to use anInGaAs

Avalanche Photodiode

Detector (APD)in a Geiger configuration

for single

photon

detection

.

Excited

Ps

cloud

IMAGING LENS

1312nm

radiation

Multimode

fiber

core

Transport

+

Focusing

Imaging

Positronium

Laser

excitation

and

its

detectionSlide33

Main challengeMULTIMODE BEAM focusing onto the 25mm DIAMETER InGaAs active surface:Theoretical and experimental

studies!

(The active

surface is

so much little to reduce the dark

counts rate)

2. Detection of 1312nm

photons

17/11/2014 First Year Workshop

33

Positronium

Laser

excitation

and

its

detection

I

estimated

that

, in

order

to

have

1

count

out of 10

e+

shots

,

we

should

deliver

into

the detector more

than

the

0,024%

of the

emitted

radiation

Example

of

multimode

beam

w=4mmSlide34

2. Detection of 1312nm photons17/11/2014 First Year Workshop34Positronium Laser excitation and its detection

We have

been able to plan an

optical setup that

, for every

shot, gives

us a

11

%

probability

signal

count

0,75%

probability

dark

count

IMPORTANT

Work in progress:

Several

improvement

can be

done

!!!Slide35

3.Detecting Ps n = 3laser excitationBy detecting the Ps laser ionization17/11/2014 First Year WorkshopPositronium Laser excitation and its

detectionSlide36

3.Ps ionization

BREADBOX SETUP

E

Porous

target

10V/cm

electric

field

e-

e+

Laser

UV

y

-

axis

x-

axis

e+

x

y-plane

electrode

electrode

Channel

Plate

and/or

channeltron

Ionizing

laser

t

i

n=3

excitation

detection

29ns

secondary

electrons

emission

at

the time of e+

arriving

on the target

5

ns

36

17/11/2014 First Year Workshop

Positronium

Laser

excitation

and

its

detectionSlide37

E

1064=10 mJ

37

3.Ps laser

ionization

Without

1064nm pulse

With 1064

pulse

n

=1

n=2

n=3

n=2

Ionized

Ps

Populations

Populations

Time(ns)

Time(ns)

n=3

n

=1

By

sending

a

1064nm laser

pulse

simultaneous

to the

exciting

one

(205nm)

we

can

ionize

a

fraction

of the n=3

excited

Ps

17/11/2014 First Year Workshop

Positronium

Laser

excitation

and

its

detectionSlide38

3.Ps ionization

BREADBOX SETUP

E

Porous

target

10V/cm

electric

field

e-

e+

Laser

UV

y

-

axis

x-

axis

e+

x

y-plane

electrode

electrode

Channel

Plate

and/or

channeltron

Laser

IR

:

Rydberg

excitation

Ionizing

laser

t

i

With a

resonant

IR:

Rydberg

excitation

detection

n=3

excitation

detection

29ns

secondary

electrons

emission

at

the time of e+

arriving

on the target

5

ns

38

17/11/2014 First Year Workshop

Positronium

Laser

excitation

and

its

detectionSlide39

The work goes on!17/11/2014 First Year Workshop39Improve my simulation with more and more physics.

Simulate the laser

ionization.

Study more in depth

the detection of the laser Ps excitation and find

the best way to perform it.

Carry on my work at CERN, in Geneva,

where

AEgIS

apparatus

and

BreadBox

are

placed

.Slide40

Thank you for your attention

Some of my

AEgIS adventure mates inside the AEgIS

experimental zoneSlide41

ChallengesMultimode beam focusing (at the fiber exit), we empirically estimated a coefficient

strictly related

to this

Focus

it

onto

the 25

m

m

diameter

InGaAs

active

surface

(so

little

to reduce the dark

counts

rate

)

2.

Detection

of 1312nm

photons

17/11/2014 First Year Workshop

41

Positronium

Laser

excitation

and

its

detection

I

estimated

that

, in

order

to

have

1

count

out of 10

e+

shots

,

we

should

deliver

into

the detector more

than

the

0,024%

of the

emitted

radiation

Example

of

multimode

beam

w=4mmSlide42

17/11/2014 First Year Workshop42The role of the Positronium in the AEgIS experimentThe Positronium termalization

A

fraction of the Ps exiting the target is

thermalized

into the target pores

PRL 104, 243401 (

2010), Sebastiano Mariazzi,

Paolo

Bettotti

,

and Roberto S.

Brusa,

“

Positronium

Cooling and Emission in Vacuum from

Nanochannels

at Cryogenic

Temperature

”