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MA inzer MI krotron MAMI : A precision accelerator for nucleon structure investigations. Kurt Aulenbacher Reactor Training Course U-South Carolina May, 28, 2008. l : Wavelength. d: object size. d:. required resolution. l < d. l :. Lightwaves and particle waves. l :.

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MA inzer MI krotron MAMI : A precision accelerator for nucleon structure investigations

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Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

MAinzer MIkrotron MAMI:

A precision accelerator

for nucleon structure investigations

Kurt Aulenbacher

Reactor Training Course

U-South Carolina

May, 28, 2008


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

l: Wavelength

d: object size

d:

required resolution

l < d


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

l:

Lightwaves and particle waves

l:

visible light : l=400 – 700nm

For particle-waves l=h/p :

E~100keV: electron microscope

E~1000MeV: ‚nucleon‘ structure ‚microscope‘


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

nucleus: a few 10-15 m

(0,0001 × Diameter of Atom)

Atom

Kern


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

e

Nucleus, z.B. Helium:

Proton(1919) and Neutron(1931) (Nucleons)

very complicated

‚many body‘

system

n

p

p

n

Electron(1898)

Proton: 10-15m, charge e+

Neutron: 10-15m, „neutral“

(pointlike ,

charge e-)


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

UHV ~ -100.000V

ElektrostaticAcceleration,

Vacuum

kinetic Energy of Electrons: E = 100.000eV

( d.h. v= 54,8% •c = 164.350km/s

l = 4 • 10-12m )


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

25.000 W

Power

Microwave Resonating Structure with

longitudinal field components and

appr. phase shifts

…allows for nearly continous energy

transfer from field to particle!


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

surf


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

surf


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

surf


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

surfin’ on

the wave


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Linac Section

2 Meter, 25.000W cw Hf, 1.800.000eV


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Achieving several hundred MeV

by brute force: LINAC

For c.w. 800MeV required: (LINAC):

- ca. 400 Sections

- ca. 1km length

- 15MWc.w. high frequency power


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

2 Dipole Magnets + n LINAC Passages

Much more efficient:

The RaceTrack Mikrotron (RTM)

z.B.: LINAC: 7,5MeV, 90Turns

675MeV total ( 125kW Hf-Power)


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Three stage acceleration


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Operating since 1990 for more than 100000 hours

RTM 2

51 Rezirkulationen

180MeV

RTM 1

18 Rezirkulationen

15MeV

RTM 3

90 Rezirkulationen

850MeV

LINAC

3.5MeV

Elektronenquelle

100keV


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

1990-2006:MAMI-B

450 Tonnen, 1.28T

still not enough: 1500 MeV desired!MAMI-C


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

250 to

250 to

2000 to

2000 to

450 to

450 to

250 to

250 to

The double sided microtron

(K.H. Kaiser et al.)

43 Turns, 855MeV 1,5GeV


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

855MeV 1500MeV

Harmonic Double Sided Microtron Mikrotron (HDSM)


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

The HDSM, a world wide unique microtron variant

Successful start up: 19. Dezember 2006


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

2

1

Ein, pin, Sin

3

Beispiel:

E=1508MeV ± 0.030MeV (0.002%)

I= ~ pA – 100mA

Strahlposition konstant auf ~ 10mm

Ei, pi, Si

Eout, pout, Sout

?

knowing 1 + 2 + 3:-get to know

Koinzidenz-Experiments need cw-beams !

The Goal: Understanding the ‚Nucleon‘

“Vielkörperstruktur stark wechselwirkender Systeme”

Nukleon (Proton, Neutron) ~ 10-15m

?


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Das KAOS Spektrometer = Nachweis von Kaonen


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Grundriss von

MAMI C

(ca. 6500 Stunden Betrieb pro Jahr)

Diplomanden und Doktoranden

in experimenteller und theoretischer

Kern- und Teilchenphysik, Beschleunigerphysik


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

MAinzer MIkrotron MAMI:

Practical Training: Irradiation and

induced radioactivy

Kurt Aulenbacher

Reactor Training Course

U-South Carolina

May, 28, 2008


Our program this afternoon two groups exchanging after about 1 hour

Irradiation of samples with MAMI at 855MeV and simultaneous measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

Investigation/identifaction of induced radioactivity: by gamma spectroscopy

Our program this afternoonTwo groups, exchanging after about 1 hour


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Hier sind wir !

Aerial view:

RTM 1 + 2

RTM 3

Accelerator and experiments are completely underground

typically 10-15 meters deep below ground level!


Radiation and radioisotopes at mami

high power (150kW), high energy particle sourceno persons allowed in areas where accelerator operates

secondary radiation : gamma rays (Bremsstrahlung up to 1500MeV)

tertiary radiation: Photoneutrons (up to 1000MeV)

neutral particles are more difficult to shield due to missing continous ionisation!

Primary radiation disappears after shutdown, induced radioistopes may persist!

Radiation and Radioisotopes at MAMI


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Example:Operation modus

I. MAMI-B

(Halle A + B + C)

Sperrbereich (’cut off’ area )

permanent cut off

due to induced radioactivity


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Op-modus

II. Exp op.:

(Spektrometerhalle)

100mA bei 1.500.000.000eV

= 150kW Leistung


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Rückl.

Vorl

300kW High power beam dump ()

Al-beads/Water (Vol60/40Strahlungslänge 14cm)

Transferefficiency Beam-powerwater >95%

Shielding 1.5 Meter heavy concrete + 6meter soil. (upwards),


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

p

High energy

accelerators E>100MeV

have very complicated

radiation field.

Proton worse than

than electron.

Electrons (primary)

Bremsstrahlung (secondary)

Photohadrons (tertiary)

Neutral components

are difficult to shield

against:

Photons and Neutrons

e


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Charged particles are easy to shield !

…but electrons create (neutral) gamma radiation


Interaction gamma radiation

Interaction Gamma-radiation

  • Photoeffect: s~E-7/2, ~Z4

    • dominant for E < 100 keV

    • efficient with high nuclear charge Z

    • Elektronen der K-Schale

  • Comptonscattering: s~E-1, ~ Z/A

    • dominant 100 keV < E < 10 MeV

  • Paircreation: s~ln(E) (0<1MeV) ~Z2

    • dominant ~ 10 MeV < E

    • Absorbermaterial mit hoher Ordnungszahl


Sum of cross sections and cascade

Sum of cross sections and cascade

High energies: Pair creation dominant:

ge++e-2g2e++2e-4g4e++4e-

typical length scale: ‚radiation length‘

Pb: 0.56cm/Fe:1.76cm/

heavy concrete: 5cm /Water 36cm


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Pb d = 1,27 cm


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

Pair creation leads to a large

number of ionizing particles

dose increases (at first)

with shielding thickness.

In deeper layers main energy

dissipation by compton scattering

exponetial damping of energy

flux and associated dose.

Typical attenuation constant:

l=1/(50cm2*g-1)

6 GeV Elektronen

Due to relativsitic effect energy transport remains concentrated

in narrow forward cone

Shielding thickness at MAMI in forward direction

at least 5 Meter heavy concrete (or äquivalent)

lateral: 2 Meter


Photo neutrons

Photo-Neutrons

Photo-Neutrons for Eg< 100 MeV by

Giant resonance neutrons!

for >170MeV:HE-neutrons

by Pion production

p+gp++n

These are much more difficult to

shield!


Dose rate behind thick shielding

Dose rate behind thick shielding

mFL … Massenbelegung

λ(Q;E)Abschwächungskonstante

d … Abstand zum Strahlungsort

we are here…

Liefert a.a.O. 54mSv/h bei 150 Watt.


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

X1 area in forward direction of

(low power) beam dump


Ma inzer mi krotron mami a precision accelerator for nucleon structure investigations

X1 area is

accessible ‚controlled area

during beam dump

operation. (1meter iron+

2 Meters heavy concrete

shielding)

Todays exercise:

I) comparison of

standard neutron monitor

with ‚wide range‘ detector

II) investigation of irradiated

samples by g-spectroscopy

Low power beam-set-up beam dump:

irradiation of test samples (Cu,Fe,Al)


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