introduction to accelerator physics · 24.07.2017 1 introduction to accelerator physics part 1...

24.07.2017

1

Introduction to Accelerator PhysicsPart 1

Pedro Castro / Accelerator Physics Group (MPY)Introduction to Accelerator PhysicsDESY, 24th July 2017

Pedro Castro | Introduction to Accelerator Physics | 24th July 2017 | Page 2

DESY CERN

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Applications of accelerators


Applications of Accelerators (1)

Particle colliders for High Energy Physics (HEP) experiments

Fixed target experiments

Two beams collider experiments

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Particle colliders for High Energy Physics experiments

Example: the Large Hadron Collider (LHC) at CERN

superconducting magnets(inside a cryostat)

built between 2001 and 2009Higgs discovery: July 2012

8.6 km

Mont BlancLake Geneva Geneva


> About 120 accelerators for research in “nuclear and particle physics”

Worldwide …

http://en.wikipedia.org/wiki/List_of_accelerators_in_particle_physics

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Light sources for biology, physics, chemistry… experiments



B

Light sources for biology, physics, chemistry… experiments

Electromagnet

• structural analysis of crystalline materials• X-ray crystallography (of proteins)• X-ray microscopy• X-ray absorption (or emission) spectroscopy• …

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7 GeV

Example: Positron-Elektron-Tandem-Ring-Anlage (PETRA)‘positron-electron tandem ring accelerator’ at DESY

built between 1976 and 1978HEP experiments: 1978-1986

JADE CELLO,PLUTO

TASSOMARK J

0.5 GeVe-/e+

e+e- collisionsat 2 x 19 GeV

gluon discovery: 1979

2.3 km long


7 GeV


built between 1976 and 1978HEP experiments: 1978-1986gluon discovery: 1979

40 GeVprotons

12 GeVe-/e+

HERA

protons

pre-accelerator for HERA 1987-2007synchrotron radiation since 1987

0.5 GeVe-/e+2.3 km long

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e-/e+


pre-accelerator for HERA 1987-2007synchrotron radiation since 1987PETRA III since 2009

Max von Laue hall300 m

2.3 km long


e-

e-

photons

14 beamlines30 exp. stations

Max von Laue hall

http://photon-science.desy.de/facilities/petra_iii/beamlines/index_eng.html

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pre-accelerator for HERA 1987-2007synchrotron radiation since 1987PETRA III since 2009PETRA III Extension from 2014

e-/e+


2.3 km long

hall nord

hall east



> About 70 electron storage rings and electron linear accelerators used as light sources (so-called ‘synchrotron radiation sources’)

Worldwide …

http://en.wikipedia.org/wiki/List_of_synchrotron_radiation_facilities

http://en.wikipedia.org/wiki/List_of_accelerators_in_particle_physics

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For radioisotope production


For radiotherapy and radiosurgery:• x-rays and gamma-rays

• ions (from protons to atoms with atomic number up to 18, Argon)

• neutrons

proton beam + stable isotopetransmutation

radioactive isotope

Accelerators in medicine


For example:


18 MeV proton acceleratorcyclotron



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For example: p

Oxygen-18 + positron

97% of decays


18 MeV proton accelerator Oxygen-18 (stable)target

Fluorine-18 (half-life time = 110 min.)

(transmutation)




For example: p

Fluorine-18 (half-life time = 110 min.)


18 MeV proton accelerator Oxygen-18target

Fludeoxyglucose (18F)

(transmutation)



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Positron EmissionTomography (PET)


detectors

!

!


PET

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Positron EmissionTomography (PET)


detectors

!

!




Worldwide …

> More than 7,000 accelerators for medicineradiotherapy (>7,500), radioisotope production (200)

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For industrial applications:


approx. numbers from 2007 (worldwide)

ApplicationIon implantation ~ 9500Electron cutting and welding ~ 4500Electron beam and x-ray irradiators ~ 2000Ion beam analysis (including AMS) ~ 200Radioisotope production (including PET) ~ 900Nondestructive testing (including security) ~ 650Neutron generators (including sealed tubes) ~ 1000

with energies up to 15 MeV


For industrial applications:an example: electron beam welding

‘deep welding effect’

up to 15 cm

acceleration up to 60-200 keV


magnets as‘focusing lenses’as well as‘deflectors’

electron beam

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ion implantation (>9,000) , electron cutting and welding (>4,000) …> More than 18,000 industrial accelerators

Worldwide …





ion implantation (>9,000) , electron cutting and welding (>4,000) …> More than 18,000 industrial accelerators

< 1%

Worldwide …

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> More than 7,000 accelerators for medicine

> More than 18,000 industrial acceleratorsion implantation (>9,000) , electron cutting and welding (>4,000) …

radiotherapy (>7,500), radioisotope production (200)

Worldwide …


Many millions of television sets, oscilloscopes using CRTs (Cathode Ray Tube)


TV

oscilloscope

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Many millions of television sets, oscilloscopes using CRTs (Cathode Ray Tube)


acceleration

magnets as ‘focusing lenses’as well as ‘deflectors’

25 frames / s

625lines



X-ray tubesDC high voltage (20-150 kV)

VACUUM

braking radiationor bremsstrahlung

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Working with accelerators in the control room …

…requires:

- a lot of (accelerator) physics knowledge

- a lot of (accelerator) engineering knowledge

- some Sherlock Holmes’ skills


The case begins…

Accelerator Control RoomHamburg, DESYSat. 12th June 20102 o’clock a.m.PETRA runs with a beam

current of 75 mA

02:24 a.m.: beam lost

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Circular accelerators: the synchrotron

vacuum chamberbending magnet

accelerating device

injector

straight sectionsbeam


Dipole magnet

beam

! dipole magnets: tomorrow

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vacuum chamberbending magnet

accelerating device

injector

straight sections

! radiofrequency acceleration: tomorrow


Low Energy Antiproton Ring (LEAR) at CERN (built in 1982)


vacuum chamber

accelerating device

bending magnet

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. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

B (perpendicular)

R


charge velocity

of the particle

magnetic field

momentum

"# $ %&#%' $ ()# * +

+ , )# → " $ ()+

(circular motion) "# , )# → " $ /)0

1(+ $ /)

1 → 1 $ /)(+


vacuum chambermagnet

accelerating device

injector

straight sections


(circular motion)

+ , )# → " $ ()+

"# , )# → " $ /)0

1(+ $ /)

1 → 1 $ /)(+ $ 2345'64'

! increase B synchronouslywith & $ /) of particle

1

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DESY (Deutsches Elektronen Synchrotron)

DESY: German electron synchrotron


DESY (Deutsches Elektronen Synchrotron)

DESY: German electron synchrotron, 1964, 7.4 GeV

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The Main Accelerator Control Room

beam current [mA]

time

Hamburg, DESYSat. 12th June 2010




PETRA runs with beam around the clock

17th July 2015 16:45

[mA]

building 25f, HASYLAB

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PETRA runs with beam around the clock

17th July 2015 16:45

[mA]

24 hours


An example of PETRA running with ‘top-up’ modus on/off

7~1.3hours

top-up modus

21st July 2015 09:35 - 11:15

beam current [mA]

time

beam lifetime

< $ <=>? !

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γγγγbremsstrahlung

scattering with the Coulomb field of a gas atom→ the electron is deflected and lost inthe surrounding vacuum chamber

-

E > 6 GeVE < 6 GeV

electrons can gain or loose energy→ called Touchek effect→ depends on the density of the electronbunch

large energy loss that leads to particle loss

bunch

Beam lifetime

rest gasscattering

Coulomb scatteringbetween two electronsfrom the same bunch

The lifetime of an electron beam is mainly limited by two effects:

-


An example of PETRA running with ‘top-up’ modus on/off

7~1.3hours

top-up modus

21st July 2015 09:35 - 11:15

beam current [mA]

time

beam lifetime

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electrons injected in PETRA

‘top-up’ modus

~0.9 mA = 1%

beam current [mA]

time


What are the advantages of running in ‘top-up’ modus?

• stable intensity conditions for measurements• constant heat load on optical components (mirrors, filters, crystals…)

" stable photon beam angle and position (‘pointing stability’)" stable wavelength

• constant heat load on accelerator vacuum chamber• increased stability of all systems• diagnostics: small dynamic range

‘top-up’ modus

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The Main Accelerator Control Room

beam current [mA]

time





Run number 4: 60 Bunches; 23rd – 30th March, 2011

magnetpower supply

power off incrate at DORIS

RF??

top-uptiming problems

RF??beam losswithout dump

RF problemsand longitudinalinstabilities

vertical beam blow up

RF circulatorwater cooling

RF??

RF circulatorwater cooling

One example of PETRA run over 7 days

Source: K. Balewski (MAC report 2011)

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http://ttfinfo.desy.de/petra/show.jsp?dir=/2010/23/11.06_n&pos=2010-06-12T02:26:30

The link to the electronic logbook:

Beam lost at 02:24 a.m.

What to do?


The Machine Protection System status from 12th June 2010 at 02:26

12th June 2010 02:26

The first suspect released: MPS is not guilty

• vacuum system ok• magnet system ok• radio-frequency ok• water cooling ok…“all systems up and running”

• vacuum system ok• magnet system ok• radio-frequency ok• water cooling ok…“all systems up and running”

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Electrons can be injected but cannot be stored !

beam current at injectionbeam current after a few turns

injection problemoraperture problem?

beamcurrent

time

500 µs ≈ 65 turns


Next suspect: injection

stored beam reference trajectory

vacuum chamber

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injected beam

stored beam

bending magnet



dipoledipoledipole

stored beam

septumhomogeneus fieldfree field region

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Next suspect: injection + accumulation

dipoledipoledipole

stored beam

septuminjected beam



dipoledipoledipole

stored beam

septuminjected beam

PETRAseptum

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septum at the Proton Synchrotron Booster (PSB) at CERN

homogeneus fieldfree field region

beaminjected beamstored beam


(1)

(2)

(3)


stored beam

septum

kicker(very fast dipole)



injected beam

time

kickerfield

~20 µs


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Electrons can be injected but cannot be stored !

beam current at injectionbeam current after a few turns

injection problemoraperture problem?

beamcurrent

time

500 µs ≈ 65 turns


Next suspect: an aperture problem


02:24 a.m.: beam lost07:00 a.m.: visual inspection

in accelerator

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Next suspect: the new octant in ‘Max von Laue hall’

e-


e-


e-beam

22.5 m

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Undulator PU 10

undulator field lines




in new octant

+NS

NS

permanentmagnets


Undulator PU 10




in new octant

electrons

photons

undulator


beam+N

S

NS

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Undulator PU 10

very flat undulator vacuum chambers


7 mm

9 mm




in new octant

beam+N

S

NS


a couple of months earlier…

vacuum chamber


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citation from the logbook: “What we have tried so far: …”

citation from the logbook: “Visual inspection of new octant: no findings”

timeof entries




in new octant11:52 a.m.: start aperture scan


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Need of focusing

beam / bunch

vacuum chambermagnet

accelerating device

injector

straight sections

pr

beam

we need to focus the beam !


Quadrupole magnets

quadrupole magnet:

B

beam

beam

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Quadrupole magnets

quadrupole magnet:four iron pole shoes of hyperbolic contour

hyperbola

x

y

xgBy ⋅−=

ygBx ⋅=

)gradient quadrupole ( 20

RIg µ

=

RB


Quadrupole magnets

xgFxgB xy ⋅−=⇒⋅−=

x

y

B

"# "#

"# $ ()# * + (Lorentz force)

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Classical mechanics: harmonic oscillator

restoring force:

" $ $%&


Quadrupole magnets

xgFxgB xy ⋅−=⇒⋅−=

ygFygB yx ⋅=⇒⋅=

focusing !

defocusing

x

y

B "'

"'

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In light optics…

defocusinglens

focusinglens

light rays

1(∗ $ 1

(*+ 1

(,$ %

(*(,

(: focal length

(light optics)(∗: systemfocal length

1(∗ $ %

(0 . 0if (* $ $(, $ (


Quadrupole magnets

QD + QF = net focusing effect:

charged particle

defocusingquadrupole(rotated 90°)

focusingquadrupole

center of quadrupoles

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Quadrupole magnets

B B

N

N

S

S

I

I

II

vertical defocusinghorizontal focusing

vertical focusinghorizontal defocusing

rotated 90°I = -I


Quadrupole magnets


focusingquadrupole

defocusingquadrupole

beam

y-plane:


focusingquadrupole

beam

x-plane:

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Quadrupole magnets



focusingquadrupole

beam

x-plane:


focusingquadrupole

QF QD QF QD QF QD QF QD QF QD


Circular accelerator

cell

dipolemagnet

dipolemagnet


focusingquadrupole

focusingquadrupole

beam

PETRA

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Circular accelerator

cell

dipolemagnet

dipolemagnet


focusingquadrupole

focusingquadrupole

beam

corrector dipole

corrector dipole

corrector dipole




in new octant11:52 a.m.: start aperture scan


focusingquadrupole


beam


corrector dipole 184 hor. corrector dipoles194 ver. corrector dipoles

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First useful hint: aperture problem

Beam position monitor



in new octant11:52 a.m.: start aperture scan13:20 a.m.: beam stored

244 beam position monitors


First useful hint: aperture problem

horizontalbeam pos.[mm]

verticalbeam pos.[mm]

N

S

EW

NENW

SESW

W N E S




2.3 km

244 monitors

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First useful hint: horizontal aperture problem


verticalbeam pos.[mm]

N

S

EW

NENW

SESW

W N E S




244 monitors

radiofrequencysystems



N

S

EW

NENW

SESW





focusingquadrupole


beam

corrector dipole

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N

S

EW

NENW

SESW

W N E S

new octant




after‘flattening’the orbit

244 monitors


citation from the logbook: “the problem is at the end of the new octant”

horizontal aperture problem in the new octant

second hint: vacuum pressure raise in the new octant

beam current [mA] vacuum pressure [mb]

beam current

vacuum pressure

vacuum pressure

02:24 a.m.beam lost

aperture scan+ trajectory corrections

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horizontal aperture problem in the new octant

second hint: vacuum pressure raise in the new octant

beam current [mA] vacuum pressure [mb]

beam current

vacuum pressure

vacuum pressure

02:24 a.m.

beam

60 m

PU13 PU14


endoscope

visual inspection inside the vacuum chamber…

beam

PU13 PU14

beam

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endoscope


beam

PU13 PU14

vacuumbellows

beam beam



vacuumbellows

RF fingers

beam

beam

an example of vaccum bellows

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the problem was found: RF fingers

beam

beam


electric field of a relativistic particle

e

) $ 00 $ 0

1

) $ 020 ≅ 1

1e

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e

1

1 $ (445=

61 $ 0071 $ 00 sin0 ; </0>0

>#>

! $ 11 $ 00

) $ 02

1?e z

;cylindrical coordinates

) $ 00 $ 0



e

1

1 $ (445=

61 $ 0071 $ 00 sin0 ; </0>0

>#>

! $ 11 $ 00

) $ 02

1?e z

! $ 10 $ 0

1 $ (445=

1>0

>#>


) $ 00 $ 0

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e

! $ 10 $ 0

1

1 $ (445=

61 $ 0071 $ 00 sin0 ; </0>0

>#>

! $ 11 $ 00

1@ ; $ 0 $ (445=

1!0>0

>#>

1A ; $ 42 $ (

445= !>0

>#>

1 $ (445=

1>0

>#>

) $ 02

1?e z


) $ 00 $ 0



e

1

1 $ (445=

61 $ 0071 $ 00 sin0 ; </0>0

>#>

! $ 11 $ 00

! ≫ 10 ≅ 1

1e

1@ ; $ 0 $ (445=

1!0>0

>#>

1A ; $ 42 $ (

445= !>0

>#>

! → ∞ 0

! → ∞ ∞

z

! $ 10 $ 0

1 $ (445=

1>0

>#>

) $ 020 ≅ 1

) $ 00 $ 0

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RF fingers and wakefields

vacuum chamber wall

beam

+ +++ +

+ +++ +

mirror currents

1



vacuum chamber wall

beam

+ +++ +

+ +++ +

mirror currents

RF fingers

beam

RF fingers

1

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beam



RF fingers: improvements doneold RF fingers were tilted outwards by 2 degrees

new RF fingers have stronger tilt, more tension

new design withRF fingers outside

beam

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Summing-up of this part

accelerator physicswakefields, RF shielding (RF fingers)

Touchek effect (limiting beam lifetime)


basic components

dipole, quadrupole, undulator magnets, corrector dipolesinjection system (kickers and septum)

vacuum pumps, vacuum pressure monitorsbeam position monitors

basic conceptsin operation

top-up modusaperture scanstrajectory (orbit) corrections

‘collective effects’

rest gas scattering (limiting beam lifetime)

vacuum chambers, bellows


[email protected]

Thank you for your attention

introduction to accelerator physics · 24.07.2017 1 introduction to accelerator physics part 1...

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