W. Udo Schröder, 2007 Nuclear Experiment 1. W. Udo Schröder, 2007 Nuclear Experiment 2 Probes for Nuclei and Nuclear Processes To “see” an object, the.

W. Udo Schröder, 2007

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Probes for Nuclei and Nuclear ProcessesProbes for Nuclei and Nuclear Processes

To “see” an object, the wavelength of the light used must be shorter than the dimensions d of the object. (DeBroglie: p=ħk=ħ2/Rutherford’s scattering experimentsdNucleus~ few 10-15 m ~ fm

Need light of wave length 1 fm, or photon energy

2 2 2 22

2 2

4 2 2

2

2002 6 1.2

1

200 2

2 2 2 1.8

8

( ) ,

0 10 1

. . :

81

0.

,

Matter waves massive m particle e g proto

c MeV fmE pc kc GeV

fm

k ck MeV fmpE

m m mc GeV

MeV fmGeV

G fmeV

n

Photons not easily available in nature

Can be made with charged particle accelerators


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Elements of a Generic Nuclear ExperimentElements of a Generic Nuclear Experiment

A: Studying natural radioactivity (cosmic rays, terrestrial active samples)

B: Inducing nuclear reactions in accelerator experiments

Particle Accelerator produces fast projectile nucleiProjectile nuclei interact with target nucleiReaction products are

a) collected and measured off line, b) measured on line with radiation detectors

Detector signals are electronically processed

Ion Source Accelerator Target

Detectors

Vacuum ChamberVacuum Beam Transport


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Ionization ProcessIonization Process

1. e- impact (gaseous ionization)

• hot cathode arc• discharge in axial magnetic field

(duo-plasmatron)• electron oscillation discharge

(Penning ion source) (PIG)• radio-frequency electrode-less

discharge (ECR)• electron beam induced discharge

(EBIS)

2. ion impact• charge exchange• sputtering

e-/ion beam

- +q-

discharge

-+q+

Acceleration possible for charged particles ionize neutral atoms


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Electron Cyclotron Resonance (ECR) Source Electron Cyclotron Resonance (ECR) Source

“Venus”

Making an e-/ion plasma


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Principle of Electrostatic AcceleratorsPrinciple of Electrostatic Accelerators

Van de Graaff, 1929

Operating limitations: 2 MV terminal voltage in air, 18-20 MV in pressure tank with insulating gas (SF6 or gas mixture N2, CO2)

Acceleration tube has equipotential plates connected by resistor chain (R), ramping field down.

Typical for a CN:

7-8 MV terminal voltage

+

-

R

R

R

R

R

R

R

+

++

+

+

+

+

+

+

+

+

+

+

+

q+

Charger 10 -4C/m2

Corona Points 20kV

+ HV Terminal

Ion Source

Acceler-ation Tube insulating

Charging Belt/ Pelletron

-Ground Plate

Conducting Sphere

+


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““Emperor” (MP) TandemEmperor” (MP) Tandem

MP Tandem15 MV

90o Deflection/Analyzing Magnet

Vacuum Beam Line

Ion Source

@Yale, BNL, TUNL, FSU, @Yale, BNL, TUNL, FSU, Seattle,…, SUNY Seattle,…, SUNY Geneseo,…Geneseo,…many around the world.many around the world.

Munich University TandemMunich University Tandem

Quadrupole Magnet

Pumping Station


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Charged Particles in Electromagnetic FieldsCharged Particles in Electromagnetic Fields

0

0

: ( ), ( )

. ,

0 :

,

,

Lorentz Force fields electric E magnetic B

F q E v B particle el charge q velocity v

E F p q v B

p q r B orbit radius r r B

pp q r B equilibrium orbit at r

qB

p mv v r

ParticleCyqB

mclotron Frequency

B: Magnetic guiding field

vr

Charged particles in electromagnetic fields follow curvilinear trajectories used to guide particles “optically” with magnetic beam transport system

q

B


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Electrodynamic Accelerators: CyclotronElectrodynamic Accelerators: Cyclotron

0

Cyclotron Frequenc

qB same for all v

m

y

field

2

max

2

2

qB

Maximum Ener

m

gy

qK

R

A

Relativistic effects: m W = + moc2 shape B field to compensate. Defocusing corrected with sectors and fringe field.

+-E

Electrodynamic linear (LINAC) or cyclic accelerators(cyclotrons,synchrotons)

Cyclotrons at BNL, LBL Berkeley, MSU, Texas A&M, …., many around the world (Catania, GANIL)

Acceleration, if field= 0

Equilibrium orbit r: p = qBr

maximum pmax = qBR


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CERN Proton LinacCERN Proton Linac


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11Experimental Setup: Neutron Time-of-Flight Experimental Setup: Neutron Time-of-Flight

MeasurementMeasurement

Experiment at GANIL 29 A MeV 208Pb 197Au

Scatter Chamber

Beam

Line

Ele

ctro

nic

s R

ack

NeutronDetector


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Particle ID: Resolution in Z , A, E

Nuclear Radiation DetectorsNuclear Radiation Detectors

Si Telescope Massive Reaction Products SiSiCsI Telescope (Light Particles)

HeLiBe

NaNe

F

O

N

C

B

20Ne + 12C @ 20.5 MeV/u - lab = 12°


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THE CHIMERA DETECTOR

THE CHIMERA DETECTOR

Chimera mechanical structure 1m

1°

30°

REVERSE EXPERIMENTAL APPARATUS

TARGETBEAM

Experimental Method

E-E ChargeE-E E-TOF Velocity, MassPulse shape Method LCP

Basic element Si (300m) + CsI(Tl) telescope

Primary experimental observables

TOF t 1 nsKinetic energy, velocityE/E Light charged particles 2%Heavy ions 1%

Total solid angle /4

94%

Granularity 1192 modules

Angular range 1°< < 176°

Detection threshold

<0.5 MeV/A for H.I. 1 MeV/A for LCP

CHIMERA characteristic features

688 telescopes

Laboratori del Sud, Catania/Italy


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Secondary-Beam FacilitiesSecondary-Beam Facilities

2 principles:

A) Isotope Separator On Line Dump intense beam into very thick production target, extract volatile reaction products, study radiochemistry or reaccelerate

to induce reactions in 2nd target (requires long life times: ms)GANIL-SPIRAL, EURISOL, RIA, TAMU,….

B) Fragmentation in Flight Induce fragmentation/spallation reactions in thick production target, select reaction products for experimentation: reactions

in 2nd target

GSI, RIKEN, MSU, Catania, (RIA)

G. Raciti, 2005

Primary Accelerator


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Secondary Beam ProductionSecondary Beam Production

Bombard a Be target with 1.6-GeV 58Ni projectiles from SCC LNS Catania

Particle Identification Matrix E x E

EE

E

Particle

Target


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RIA: A New Secondary-Beam FacilityRIA: A New Secondary-Beam Facility

One of 2 draft designs : MSU/NSCL proposal


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ISOLDE Facility at CERNISOLDE Facility at CERN

Primary proton beam CERN-PS

Project started @CERN in the 1960s


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Secondary-Beam AcceleratorSecondary-Beam Accelerator

Radiochemical goal (high-T chemistry, surface physics, metallurgy): produce ion beam with isotopes of only one element

Ion Source

Low-energy LINAC

Mass Separator

X1+

High Charge

Primary target: oven at 7000C – 20000C, bombarded with beams from 2 CERN accelerators (SC, PS).


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ISOLDE Mass SeparatorsISOLDE Mass Separators

High Resolution Separator

M5000 30000

M

General Purpose Separator

calculated


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Secondary ISOLDE BeamsSecondary ISOLDE Beams

Yellow: produced by ISOLDEn-rich, n-rich

Sn: A = 108 -142 low energy

O: A = 19 -22 low energy

Source: CERN/ISOLDE

ISOLDE accepts beams from several CERN accelerators (SC, PS)


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Mass Measurement with Penning TrapMass Measurement with Penning Trap

ISOLTRAP Ion motion in superposition of B and EQ fields has 3 cyclic components with frequencies C, +, -

Electric quadrupole field

0

qB

m

Cyclotron frequency

Oscillating quadrupole field EQ can excite at = 0 determine m


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Injection and AccelerationInjection and Acceleration

Transfer to accelerator

Acceleration

Injection (axial)

Ion trajectory (cyclic)


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W. Udo Schröder, 2007 Nuclear Experiment 1. W. Udo Schröder, 2007 Nuclear Experiment 2 Probes for Nuclei and Nuclear Processes To “see” an object, the.

Documents

udo schrder

generic nuclear experiment

nuclear reactions

nuclear processes

q discharge

qbr slide

e ion plasma slide

sphere slide