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 CourseU-South Carolina

May, 28, 2008

Kurt Aulenbacher , Institut für Kernphysik, Johannes Gutenberg-Universität

d:d: object size

: Wavelength

< drequired resolution


:

visible light : =400 – 700nm

Lightwaves and particle waves

For particle-waves =h/p :E~100keV: electron microscope E~1000MeV: ‚nucleon‘ structure ‚microscope‘

:


nucleus: a few 10-15 m(0,0001 × Diameter of Atom)

Atom

Kern


Electron(1898)

Nucleus, z.B. Helium:Proton(1919) and Neutron(1931) (Nucleons)

(pointlike ,charge e-)

Proton: 10-15m, charge e+

Neutron: 10-15m, „neutral“

pp

n

n

e

very complicated ‚many body‘

system


UHV ~ -100.000V

ElektrostaticAcceleration,

kinetic Energy of Electrons: E = 100.000eV( d.h. v= 54,8% •c = 164.350km/s

= 4 • 10-12m )

Vacuum


Microwave Resonating Structure with longitudinal field components and

appr. phase shifts

25.000 WPower

…allows for nearly continous energy transfer from field to particle!


surf


surfin’ onthe wave


01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

2 Meter, 25.000W cw Hf, 1.800.000eV

Linac Section


01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 3301 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

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

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33


2 Dipole Magnets + n LINAC Passages

z.B.: LINAC: 7,5MeV, 90Turns 675MeV total ( 125kW Hf-Power)

Much more efficient:The RaceTrack Mikrotron (RTM)


Three stage acceleration


RTM 390 Rezirkulationen

850MeV3.5MeV


15MeV


180MeV

LINAC

Elektronenquelle100keV

Operating since 1990 for more than 100000 hours


1990-2006:MAMI-B

450 Tonnen, 1.28T

still not enough: 1500 MeV desired!MAMI-C


2000 to 2000 to

250 to

250 to250 to

250 to

The double sided microtron(K.H. Kaiser et al.)

43 Turns, 855MeV 1,5GeV

450 to450 to


855MeV 1500MeVHarmonic Double Sided Microtron Mikrotron (HDSM)

LINAC I (4 .90G Hz)

LINAC II (2.45G Hz)

10m

43 Um läufeB =1.539Tm ax

In jektion 855M eV

Extraktion 1507M eV

No. 2

No. 1No. 4

No. 3

M atching Sektion4.90G Hz


Successful start up: 19. Dezember 2006

The HDSM, a world wide unique microtron variant


Beispiel:E=1508MeV ± 0.030MeV (0.002%)I= ~ pA – 100AStrahlposition konstant auf ~ 10m

1

3

2?

The Goal: Understanding the ‚Nucleon‘

“Vielkörperstruktur stark wechselwirkender Systeme”

knowing 1 + 2 + 3:-get to know ?Koinzidenz-Experiments need cw-beams !

Nukleon (Proton, Neutron) ~ 10-15m


Das KAOS Spektrometer = Nachweis von Kaonen


Grundriss vonMAMI C

(ca. 6500 Stunden Betrieb pro Jahr)

Diplomanden und Doktorandenin experimenteller und theoretischerKern- und Teilchenphysik, Beschleunigerphysik

MAinzer MIkrotron MAMI:Practical Training: Irradiation and

induced radioactivy

Kurt Aulenbacher

Reactor Training CourseU-South Carolina

May, 28, 2008


Our program this afternoonTwo 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


Aerial view:

RTM 1 + 2

RTM 3

Accelerator and experiments are completely underground typically 10-15 meters deep below ground level!

Hier sind wir !


Radiation and Radioisotopes at MAMI

• high power (150kW), high energy particle sourceno 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!


I. MAMI-B (Halle A + B + C)

Example:Operation modus

Sperrbereich (’cut off’ area )

permanent cut off due to induced radioactivity


100A bei 1.500.000.000eV= 150kW Leistung

II. Exp op.:(Spektrometerhalle)

Op-modus


300kW High power beam dump () Al-beads/Water (Vol60/40Strahlungslänge 14cm)Transferefficiency Beam-powerwater >95%Shielding 1.5 Meter heavy concrete + 6meter soil. (upwards),

Vorl

Rückl.


e

p

High energy accelerators E>100MeVhave 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


Charged particles are easy to shield !…but electrons create (neutral) gamma radiation


Interaction Gamma-radiation

• Photoeffect: ~E-7/2, ~Z4

– dominant for E < 100 keV

– efficient with high nuclear charge Z

– Elektronen der K-Schale

• Comptonscattering: ~E-1, ~ Z/A– dominant 100 keV < E < 10 MeV

• Paircreation: ~ln(E) (0<1MeV) ~Z2

– dominant ~ 10 MeV < E

– Absorbermaterial mit hoher Ordnungszahl


Sum of cross sections and cascade

High energies: Pair creation dominant:

e++e-22e++2e-44e++4e-

typical length scale: ‚radiation length‘Pb: 0.56cm/Fe:1.76cm/heavy concrete: 5cm /Water 36cm

Kurt Aulenbacher , Institut für Kernphysik, Johannes Gutenberg-Universität Pb d = 1,27 cm


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 scatteringexponetial damping of energy flux and associated dose.

Typical attenuation constant: =1/(50cm2*g-1)

6 GeV Elektronen

Shielding thickness at MAMI in forward directionat least 5 Meter heavy concrete (or äquivalent)

lateral: 2 Meter

Due to relativsitic effect energy transport remains concentrated in narrow forward cone


Photo-Neutrons

Photo-Neutrons for E< 100 MeV by Giant resonance neutrons!

for >170MeV:HE-neutrons by Pion production

p++n

These are much more difficult to shield!


Dose rate behind thick shielding

d

mVFODL FL 1

*exp*~

angle/Grad 30 60 90

sand 94 g/cm2 89 g/cm2 89 g/cm2

concrete 100 g/cm2 92 g/cm2 92 g/cm2

Heavy concrete

115 g/cm2 112 g/cm2 106 g/cm2

mFL … Massenbelegungλ(;E)Abschwächungskonstanted … Abstand zum Strahlungsort

Liefert a.a.O. 54Sv/h bei 150 Watt. we are here…


X1 area in forward direction of (low power) beam dump


Low power beam-set-up beam dump: irradiation of test samples (Cu,Fe,Al)

X1 area isaccessible ‚controlled areaduring beam dump operation. (1meter iron+2 Meters heavy concrete shielding)

Todays exercise: I) comparison of standard neutron monitorwith ‚wide range‘ detectorII) investigation of irradiated samples by -spectroscopy

ma inzer mi krotron mami : a precision accelerator for nucleon structure investigations

Documents

institut fr kernphysik

johannes gutenberguniversittd

johannes gutenberguniversittl

johannes gutenberguniversittz

mev desired

mev total

charge eproton

charge e neutron