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

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

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:

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

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: 10-15m, charge e+ Neutron: 10-15m, „neutral“ e (pointlike , charge e-)

kinetic Energy of Electrons: E = 100.000eV ElektrostaticAcceleration, Vacuum UHV ~ -100.000V kinetic Energy of Electrons: E = 100.000eV ( d.h. v= 54,8% •c = 164.350km/s  l = 4 • 10-12m )

Microwave Resonating Structure with longitudinal field components and appr. phase shifts 25.000 W Power …allows for nearly continous energy transfer from field to particle!

surf

surf

surf

surfin’ on the wave

2 Meter, 25.000W cw Hf, 1.800.000eV Linac Section

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

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)

Three stage acceleration

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

still not enough: 1500 MeV desired!MAMI-C 1990-2006:MAMI-B 450 Tonnen, 1.28T still not enough: 1500 MeV desired!MAMI-C

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

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

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

Seit dem 23.02.2007 Experimentierbetrieb: 1.508GeV, max. 100mA, d.h. 151kW Strahlleistung Kurzer Hochstromtest: 50mA beam on target: >80% Fr., 23.02.2007, 12.00 bis Mo., 05.03.2007, 6.00

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

Das KAOS Spektrometer = Nachweis von Kaonen

(ca. 6500 Stunden Betrieb pro Jahr) 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

Aerial view: Hier sind wir ! 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!

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

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

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),

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

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

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

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 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.

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

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)