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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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MAinzer MIkrotron 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:

visible light : l=400 – 700nm

For particle-waves l=h/p :

E~100keV: electron microscope

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


nucleus: a few 10-15 m

(0,0001 × Diameter of Atom)

Atom

Kern


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-)


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 )


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!





surfin’ on

the wave


Linac Section

2 Meter, 25.000W cw Hf, 1.800.000eV


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


2 Dipole Magnets + n LINAC Passages

Much more efficient:

The RaceTrack Mikrotron (RTM)

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

675MeV total ( 125kW Hf-Power)



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


1990-2006:MAMI-B

450 Tonnen, 1.28T

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


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


855MeV 1500MeV

Harmonic Double Sided Microtron Mikrotron (HDSM)


The HDSM, a world wide unique microtron variant

Successful start up: 19. Dezember 2006


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

?



Grundriss von

MAMI C

(ca. 6500 Stunden Betrieb pro Jahr)

Diplomanden und Doktoranden

in experimenteller und theoretischer

Kern- und Teilchenphysik, Beschleunigerphysik


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


Hier sind wir ! measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

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 measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area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


Example:Operation modus measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

I. MAMI-B

(Halle A + B + C)

Sperrbereich (’cut off’ area )

permanent cut off

due to induced radioactivity


Op-modus measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

II. Exp op.:

(Spektrometerhalle)

100mA bei 1.500.000.000eV

= 150kW Leistung


Rückl. measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

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),


p measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

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


Charged particles are easy to shield ! measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

…but electrons create (neutral) gamma radiation


Interaction gamma radiation
Interaction Gamma-radiation measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

  • 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 measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

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


Pb d = 1,27 cm measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area


Pair creation leads to a large measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

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 measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

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 measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

mFL … Massenbelegung

λ(Q;E)Abschwächungskonstante

d … Abstand zum Strahlungsort

we are here…

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


X1 area in forward direction of measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

(low power) beam dump


X1 area is measurement of neutron radiation field in accesible area., Hall clearance and installation of ‚cut off‘ area

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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