ACCELERATOR PHYSICS I
Definition of a particle accelerator Cambridge Dictionary A Dictionary A particle accelerator accelerator is a machine which makes extremely small pieces of matter travel at very high speeds , so that scientists can study the way they behave
Encyclopædia Britannica any device that produces a beam of fast-moving, electrically charged atomic or subatomic particles.. Physicists use accelerators in fundamental particles research on the structure of nuclei, the nature of nuclear forces, and the properties of nuclei not found in nature I hope that after after this course, course, you will know better....
Definition of a particle accelerator Cambridge Dictionary A Dictionary A particle accelerator accelerator is a machine which makes extremely small pieces of matter travel at very high speeds , so that scientists can study the way they behave
Encyclopædia Britannica any device that produces a beam of fast-moving, electrically charged atomic or subatomic particles.. Physicists use accelerators in fundamental particles research on the structure of nuclei, the nature of nuclear forces, and the properties of nuclei not found in nature I hope that after after this course, course, you will know better....
Resources and Literature an introduction to PARTICLE ACCELERATO ACCELERATORS RS Edmund Wilson – Wilson – Head of CERN Accelerator School OXFORD University Press ISBN 0-19-852054-9
5th General CERN Accelerator School, CERN 94-01, 26 January 1994, 2 Volumes, edited by S.Turner http://schools.web.cern.ch/Sch http://schools.web .cern.ch/Schools/CAS/CAS_Pr ools/CAS/CAS_Proceedings.html oceedings.html
Some pictures pictures from from Rüdiger Schmidt Schmidt – Cern Head of SPS and LHC Machine Protection Working Working Group Some pictures from Klaus Wille – Wille – Professor at TU Darmstadt
Overview •
Introduction and Overview – Accelerating and bending of particles – Cockroft-Walton - Greinacher cascade – Van de Graaff – Collider vs fixed target – Luminosity – Livingston plot – The Large Hadron Collider – LHC – Event rates and multiplicities
• Accelerator basics – – – – –
•
LINAC Cyclotron Betatron Synchrotron Weak and Strong focusing
Beam dynamics and stability – – – –
Focusing Twiss matrix FODO lattice Betatron motion
Electrostatic acceleration – 1 eV : kinetic energy gained by a unit charged particle after passing an electrostatic potential of one volt – 1 eV = 1.6 x 10 -19 J
E-Field = V/d
[Joule]
eV E kin
( 1)mc 2
- V = 1 Volt + d= distance anode to kathode
mc 2 1 c 2 eV mc
V F eE e d Fd E kin eV
c
Energie [eV] Velocity Energie [eV]
Energie [Joule]
Velocity Electron [511keV/c 2]
Velocity Proton [938 MeV/c2]
1 eV
1.6 x 10-19 J
593 km/s 0.002 c
14 km/s 0.00005 c
1 keV
1.6 x 10-16 J
18730 km/s 0.062 c
438 km/s 0.0015 c
1 MeV
1.6 x 10-13 J
282128 km/s 0.94 c
13832 km/s 0.046 c
1 GeV
1.6 x 10-10 J
299792 km/s 0.9999998 c
262338 km/s 0.88 c
1 TeV
1.6 x 10-7 J
299792 km/s 0.9999999999998 c
299792 km/s 0.9999996 c
7 TeV
1.1 x 10-8 J
299792 km/s 0.999999999999997 c
299792 km/s 0.999999991 c
7 TeV (Energie of protons in the LHC accelerator – start: summer 2008):
High voltage generation: Cockroft Walton
Sir John Douglas Cockcroft
Ernest Thomas Sinton Walton
* 27 May 1897, Todmorden ,UK † 18 September 1967, Cambridge, UK
* 6 October1903, Dungarvan, Ireland † 25 June 1995, Belfast, Ireland
Nobel Price 1951 "for their pioneer work on the transmutation of atomic nuclei by artificially accelerated atomic particles"
High voltage generation: Greinacher Circuit
Heinrich Greinacher * 31 Mai 1880, St. Gallen † 17 April 1974, Bern
Cockroft- Walton High Voltage generator
Greinacher cascade
High voltage generation: Greinacher Circuit
DC
Bern 1919
AC
Greinacher circuit Greinacher cascade
original Greinacher cascade
Greinacher
Route Greinacher at Cern
First stage of an accelerator. Greinacher cascade (i.e. Cockroft-Walton) on the right. Greinacher cascade on a palm
Heinrich Greinacher Greinacher war das einzige Kind des Schuhmachermeisters Heinrich Greinacher und seiner Ehefrau Pauline geborene Münzenmayer. Er besuchte das Gymnasium in St. Gallen und studierte Physik in Zürich, Genf und Berlin. Am Konservatorium Genf ließ Greinacher sich auch zum Pianisten ausbilden. Ursprünglich deutscher Staatsbürger, wurde er 1894 in St. Gallen eingebürgert. In Berlin besuchte Greinacher Vorlesungen bei Max Planck und promovierte 1904 bei Emil Warburg. Seine Habilitation folgte 1907 an der Universität Zürich. Greinacher wurde 1912 Titularprofessor in Zürich.
Von 1924 bis 1952 war er dann ordentlicher Professor für Experimentalphysik an der Universität Bern und Direktor des Physikalischen Instituts (vormals Physikalisches Cabinett ). Die Heinrich-Greinacher-Stiftung in Bern wurde 1988 aus dem Nachlass des Ehepaars Frieda und Heinrich Greinacher gegründet. Zinserträge des Stiftungskapitals werden für den Heinrich-Greinacher-Preis und zur Förderung von Nachwuchsforschern verwendet.
Das Physikalische Institut zur Zeit von Heinrich Greinacher Das Haus wurde 1876/77 auf der grossen Schanze neben der Universität am Standort des heutigen Gebäudes für Exakte Wissenschaften gebaut.
High voltage generation: Van de Graaff Generator
The tandem Van de Graaff accelerator at Western Michigan University is used mainly for basic r esearch, applications and undergraduate instruction. Vmax = 25 MV
Tandem Van de Graaff Accelerator A tandem Van de Graaff accelerator provides a beam with twice the energy that could be achieved by one application of the high voltage. An ion source yields a beam of negative hydrogen ions by the addition of two electrons The beam of negative ions is then accelerated toward the positive high-voltage terminal. In this terminal, the particles pass through a thin carbon foil that strips off the two electrons, changing many of the negative ions back into positive ions (protons). These, now repelled by the positive terminal, are further accelerated through the second part of the tube.
Van de Graaff generator 1929: first model was demonstrated 1931: 1 MV reached 1970: 14 MV reached using a tandem Van de Graaff that used a tank of high pressure sulfur hexafluoride (SF6) gas to prevent sparking by trapping electrons. today: 25 MV tandem Van de Graaff
Robert Jemison Van de Graaff * 20. December 1901 † 16. January 1967
Van de Graaff generator being demonstrated by Robert J. Van de Graaff, himself. Joined Van de Graaff
Koffler accelerator at the Weizmann Institute of Science, Rehovot Israel
14 MV Pelletron Accelerator Mass Spectrometry (AMS) with 14C, 7Be, 10Be, 26 Al, 36Cl, 41Ca, 44Ti, 59Ni, 90Sr, 129I, 236U, 239Pu, 240Pu, 242Pu, 244Pu
From DC acceleration to RF •
Limit for DC voltages few MV – –
•
Gustaf Ising 1924 –
•
demonstrated first ring accelerator
today – – –
•
demonstrated first LINAC using RF
Ernest Lawrence 1931 –
•
proposes to use RF for acceleration
Rolf Wideröe 1928 –
•
complex devices sparks
almost all accelerators using RF LINACs as pre-accelerator Ring accelerator as main machine – e.g. LHC
future – –
LINAC – e.g. ILC, CLIC (2020? / 25??) Ring accelerator age ring (20??)
Particle accelerator First ring accelerator 1930 Ernest Lawrence in Berkeley, USA.
Ernest Lawrence * 8. August 1901 † 27. August 1958
Modern Accelerator/ Collider acceleration elements, bending magnets and particle detectors
Accelerating charged particles V Fz
E ds
z V e
E
E
z
B
Bending charged particles
FLorentz
R
dp
p
ds
p dp
dt
ds Rd
R d
dp p d p dp
d
d
p
dt
ev B e B v
1 ds p p v
R dt p eBv v R
R
dp p
dt
BR Tm 3.3356p GeV c
dp
RLHC 4.25 km p 7000 GeV B 5.5 T
LHC: B=8.4 T, not only bending magnets in tunnel, but also straight sections for acceleration,
Fix target accelerator vs. collider
Etot: 7 TeV + 7 TeV = 14 TeV Etot: 7 TeV + 0 TeV = 0.118 TeV + 6.882 TeV lost due to momentum conservation
Fix target accelerator vs. collider E1, p1 E2 , p 2
2 2 2 s (E1, p1 ) (E 2 , p2 ) E 1 E 2 p1 p 2 2 2 Etot E E p p with: ,cm 1 2 1 2 2 2 s Etot ,cm E cm
Ecm
2
E1 E2
c 1
Lorentz invariant
2 p 1 p 2
Lorentz invariant E 2 p 2 m 2
Fix Target
Collider
E1, p1 ELab , p Lab F T 2 4 2 4 2 Ecm m1c m2c 2ELabm2c E2 , p 2 m 2 , 0 E1, p1 ELab , p Lab C E cm 2E Lab E2 , p 2 E Lab , p Lab
Fix Target
Collider
E 1 7 TeV
E2 m Pr oton E 1 7 TeV
E cm
E
2 7000 1 118 Ge V
2 7000 14 ' 000 GeV
2ELabm2c 2
Livingston Plot FT 2 Ecm 2m p E Lab
1 EeV LHC
100 PeV 10 PeV Tevatron 1 PeV
SppS
100 TeV HERA
10 TeV
LEP
ISR
1 TeV 100 GeV 10 GeV 1 GeV 100 MeV 10 MeV 1 MeV 1930
1950
1970
1990
2010
Luminosity N Events s
cm2s 1
High Luminosity: find rare physics processes in finite time
N 1
nb N 1 N 2 f
4 x y
A
N 2 A 4x y
,
x y
gaussian beam profiles
Luminosity is a pure machine parameter: It can be increased by having: • many bunches nb • many particles per bunch N1 and N2 • small cross section A ; i.e. excellent focussing at interaction point • many bunch crossings per second (f =revolving frequency for 1 bunch; LHC: f=c/26.7 km = 11’228 Hz
89 s)
The biggest accelerator is the universe 1 particle/m2/s
1 particle/m2/year „knee“
10000 particles/km 2/year
LHC 1 particle/km2/year „ankle“
Cosmic ray particles bang on the higher atmosphere at energies far higher than the LHC can provide – but at low rates and unknown directions
• At the LHC 109 collisions take – place every second
ISR – Intersecting Storage Ring
Proton – Proton Collider
s=62 GeV =1.3x1032cm-2s-1
1971-1984 at Cern
HERA
Hadron Elektron R ing A nlage: Elektron-Proton collider s=340 GeV; =7.5x1031cm-2s-1; 1992 –2007 Positron Elektron Tandem R ing A nlage: s=38 GeV; =2x1030cm-2s-1; 1978 – 1990 At Deutschen Elektronen Synchrotron (DESY) in Hamburg
Tevatron
Proton – Anti-Proton collider s=2 TeV; 1987-2009 at Fermilab near Chicago, USA 32 -2 =1.7x10 cm s-1
CERN Conseille Europénne pour la R echerche Nucléaire
CERN Accelerator Chain
SPS: protons, anti-protons, heavy ions, electrons, positrons; 1974 – today SppS: proton-antiproton collider s=540GeV; =2.4x1030cm-2s-1 1981-1984 LEP: Large Electron Positron Collider s=90GeV – 208GeV; =1.3x1032cm-2s-1; 1989 – 2000 LHC: Large Hadron Collider s=14000 GeV;
=1034cm-2s-1;
2008-202x
