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MAinzer MIkrotron MAMI: A precision accelerator

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Präsentation zum Thema: "MAinzer MIkrotron MAMI: A precision accelerator"—  Präsentation transkript:

1 MAinzer MIkrotron MAMI: A precision accelerator
for nucleon structure investigations Kurt Aulenbacher Reactor Training Course U-South Carolina May, 28, 2008

2 l: Wavelength d: d: object size l < d required resolution

3 Lightwaves and particle waves
visible light : l=400 – 700nm For particle-waves l=h/p : E~100keV: electron microscope E~1000MeV: ‚nucleon‘ structure ‚microscope‘ l:

4 nucleus: a few m (0,0001 × Diameter of Atom) Atom Kern

5 Proton(1919) and Neutron(1931) (Nucleons)
Nucleus, z.B. Helium: Proton(1919) and Neutron(1931) (Nucleons) very complicated ‚many body‘ system n p p n Electron(1898) Proton: m, charge e+ Neutron: 10-15m, „neutral“ e (pointlike , charge e-)

6 kinetic Energy of Electrons: E = 100.000eV
ElektrostaticAcceleration, Vacuum UHV ~ V kinetic Energy of Electrons: E = eV ( d.h. v= 54,8% •c = km/s  l = 4 • 10-12m )

7 Microwave Resonating Structure with longitudinal field components and
appr. phase shifts W Power …allows for nearly continous energy transfer from field to particle!

8 surf

9 surf

10 surf

11 surfin’ on the wave

12 2 Meter, W cw Hf, eV Linac Section

13 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

14 The RaceTrack Mikrotron (RTM)
Much more efficient: The RaceTrack Mikrotron (RTM) 2 Dipole Magnets + n LINAC Passages z.B.: LINAC: 7,5MeV, 90Turns  675MeV total ( 125kW Hf-Power)

15 Three stage acceleration

16 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

17 still not enough: 1500 MeV desired!MAMI-C
:MAMI-B 450 Tonnen, 1.28T still not enough: 1500 MeV desired!MAMI-C

18 The double sided microtron
(K.H. Kaiser et al.) 250 to 2000 to 450 to 43 Turns, 855MeV  1,5GeV

19 Harmonic Double Sided Microtron Mikrotron (HDSM)
855MeV 1500MeV Harmonic Double Sided Microtron Mikrotron (HDSM)

20 The HDSM, a world wide unique microtron variant
Successful start up: 19. Dezember 2006

21 Seit dem 23.02.2007 Experimentierbetrieb:
1.508GeV, max. 100mA, d.h. 151kW Strahlleistung Kurzer Hochstromtest: 50mA beam on target: >80% Fr., , bis Mo., , 6.00

22 “Vielkörperstruktur stark wechselwirkender Systeme”
The Goal: Understanding the ‚Nucleon‘ “Vielkörperstruktur stark wechselwirkender Systeme” Nukleon (Proton, Neutron) ~ 10-15m ? Eout, pout, Sout 2 Ein, pin, Sin Beispiel: E=1508MeV ± 0.030MeV (0.002%) I= ~ pA – 100mA Strahlposition konstant auf ~ 10mm 1 Ei, pi, Si 3 knowing :-get to know ? Koinzidenz-Experiments need cw-beams !


24 Das KAOS Spektrometer = Nachweis von Kaonen

25 (ca. 6500 Stunden Betrieb pro Jahr)
Grundriss von MAMI C (ca Stunden Betrieb pro Jahr) Diplomanden und Doktoranden in experimenteller und theoretischer Kern- und Teilchenphysik, Beschleunigerphysik


27 MAinzer MIkrotron MAMI: Practical Training: Irradiation and
induced radioactivy Kurt Aulenbacher Reactor Training Course U-South Carolina May, 28, 2008

28 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

29 Aerial view: Hier sind wir !
RTM 1 + 2 RTM 3 Accelerator and experiments are completely underground typically meters deep below ground level!

30 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!

31 due to induced radioactivity
Example:Operation modus I. MAMI-B (Halle A + B + C) Sperrbereich (’cut off’ area ) permanent cut off due to induced radioactivity

32 II. Exp op.: (Spektrometerhalle) 100mA bei 1.500.000.000eV
Op-modus II. Exp op.: (Spektrometerhalle) 100mA bei eV = 150kW Leistung

33 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),

34 are difficult to shield
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

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

36 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

37 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

38 Pb d = 1,27 cm

39 Due to relativsitic effect energy transport remains concentrated
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

40 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!

41 Dose rate behind thick shielding
mFL … Massenbelegung λ(Q;E)Abschwächungskonstante d … Abstand zum Strahlungsort angle/Grad 30 60 90 sand 94 g/cm2 89 g/cm2 concrete 100 g/cm2 92 g/cm2 Heavy concrete 115 g/cm2 112 g/cm2 106 g/cm2 we are here… Liefert a.a.O. 54mSv/h bei 150 Watt.

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

43 accessible ‚controlled area during beam dump operation. (1meter iron+
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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