Tracking of low energy heavy ions

Antoine Drouart CEA Irfu/SPhN – [email protected] DITANET Conference 11.09 – 11.11.2011 – Sevilla

1/17

Two applications in nuclear physics

- Upstream beam tracking at medium energy (>10MeV/u)- Downstream reaction product tracking at low energy (<1MeV/u)- Event by event detection


2/17

Application : Upstream Tracking

unknown distribution

Incomingbeam

Target

θ1Scattering angleIncident angle

Position of vertexVelocity

θ0(x0,y0)

v0

perfect beamθ1

With a perfect beam track only the outgoing

particles

Large Beam emittance ~10π mm.mrad (hor+vert)

1.5m upstream 0.5m upstream On target


3/17

Effects on kinematics reconstruction

C. JOUANNE (SPHN) PHD 2002

11C+p 11C+p’ 40.6 MeV/u

11C 11C

ProtonEp

Θp

E*

WithoutBeam Tracking

WithBeam Tracking


4/17

Experimental set-up: CATS + MUST2

BEAM

2nd tracking detector

Target

7cm

MUST 2 : light particle detector (p, d, t, He, Li) (ΔE,E) or (E,t) : identification(x,y) : scatering angle


5/17

The CATS Beam Tracking DetectorsLow Pressure gas detector

Low pressure (P=4-10 Torr)gas: CF4, C3F8, iC4H10

Thin windowMylar 1.5µm

Anode

i+ i+ i+ i+ e- e- e- e-

cathodes

E If E/P high enough avalanche (>100V/cm/Torr) amplificationcharge movement induced signalelectrons are rapid fast signal

incoming ion

conducting Strips

Charge distribution positionX

10ns

600mV (after gain x200)


6/17

Basic CATS/BTD mechanics

Active area: 7x7cm2

iC4H10 @ 6Torr2x28 strips on cathodes1 fast anode signal

Ottini & al., NIM A, 431(1999) p. 476-484.


7/17

Virtues & Flaws of Low pressure detectors

- fast signal good time resolution σ = 100ps- good position resolution σ = 100µm- high detection efficiency (~100%)- large size available (>100cm2)- cheap and can be repaired- Thin : ~5µm of Mylar (from windows and cathodes)

- vulnerable to discharge : rate < 106pps- 1.5µm windows required Eion > 10MeV/u- fragile and delicate to use


8/17

Application : Downstream Tracking

Very low Energy regime <1MeV/u

The Super Separator Spectrometer S3

- Selection and transmission of low energy fusion-evaporation residues In flight mass measurement

Magnetic dipoleElectric dipole

Beam

Momentum achromat

Mass spectrometer

Final focal plane


9/17

Mass Dispersive Focal plane

Shashikant Manikonda, ANL

Momentum Achromat Mass Separator10cm

10cm

100Sn99Sn 101Sn

Q=24+ Q=23+ Q=22+Q=25+Q=26+

Distribution FWHM ~ 1.3 mm


10/17

Ions

Emissive foil(Mylar+Al, Carbon)

Secondaryelectrons

E

B

Electron detector = gaseous detector

Very low thickness< 1µm foil

Secondary emission- low energy electrons (few eV)- depends on the material (CsI…)- surface process- proportional to dE/dx

Emissive foil detector


11/17

The Se-D : Secondary electron Detector


12/17

The Se-D : Secondary electron Detector


13/17

Existing Se-D Detector

VAMOS Spectometer Focal plane size : 10 x 40 cm2

Magnetic coils

Metal testing Mask

Emissive foil

Secondary Electron Detector

Incoming ions

- <1µm of Mylar- σtime ~ 100ps- σspace ~ 600µm


14/17

Y cathode(wires)anode (wires)

X cathode(strips)

anode (wires)

X+Y 2D cathode (strips)

- similar time resolution σtime ~ 100ps- more robust- higher counting rate : up to 2.106pps

Se-D with one 2D cathode


15/17

SED2D sym. chamber of 201x138 mm2 or 68x47 1D strips - Mounted since sept 2011, time resolution on-going - AFTER-SED ASIC to connect- Spatial resolution to be done

New Prototype for S3


16/17

Conclusions & Perspectives

Upstream Beam Detectors: MWPC good time and position resolutionBUTLimited counting rate + not so thin (5µm of Mylar)

Downstream reaction product detectors: emissive foil MWPC as 1st generation 2D cathode placegood time resolution, very thin, high couting rate BUTpoor position resolution σspace ~ 600µm

To come- improve position resolution of emissive foil detector- test of other secondary electron detector : Micromegas use emissive foil detectors for upstream applications


17/17

People involved at CNA, GANIL and CEA/IRFUTechnical support & Engineering: T. Chaminade, F. Druillole, E. Monmarthe (IRFU) M. Kebbiri (IRFU), S. Damoy (GANIL), M. Riallot (IRFU), G. Fremont (GANIL)

Scientific coordinator : M. Alvarez (CNA), H. Savajols, E. Clement, F. Farget (GANIL), A. Drouart, D. Doré, T. Materna (IRFU)

Technical coordinator and analysis : B. Fernandez (CNA) , J. Pancin (GANIL), T. Papaevangleou (IRFU)And the others

Collaboration

Documents

Tracking of low energy heavy ions