Future Cold BPMs at DESY

D. Nölle, DESYCARE BPM Workshop Lüneburg, 30.11 – 1.12.2006

XFELThe EuropeanX-Ray Laser Project X-Ray Free-Electron Laser

Future Cold BPMs at DESYD. Nölle, MDI1.12.06

2D. Nölle, DESYESLS Workshop, Saclay, Oct, 2006


Motivation: X-FEL

One injector initially installed

Connection to 2nd stage upgrade included in beam distribution layout

Superconducting 20 GeV LINACWith 120 Cryomodules



Properties of XFEL radiationX-ray FEL radiation (0.2 - 14.4 keV)

– ultrashort pulse duration <100 fs (rms)– extreme pulse intensities 1012-1014 ph– coherent radiation x109

– average brilliance x104

Spontaneous radiation (20-100 keV)– ultrashort pulse duration <100 fs (rms)– high brilliance

FLASH

FLASH(seeded)

FLASH

FLASH(seeded)

Goal 30.000 Pulses/s



Just for Info: Accelerator Layout Parm’sEnergy for 0.1nm wavelength (max. design energy) 17.5 GeV (20 GeV) # of installed accelerator modules 116 # of cavities 928 Acc. Gradient (104 active modules) at 20 GeV 23.6 MV/m # of installed RF stations 29 Klystron peak power (26 active stations) 5.2 MW Loaded quality factor Qext 4.6106 RF pulse length 1.4 ms Beam pulse length 0.65ms Repetition rate 10 Hz Max. average Beam power 600 kW Unloaded cavity quality factor Q0 1010 2K cryogenic load (including transfer line losses) 1.7 kW Max. # of bunches per pulse (at 20 GeV) 3,250 (3,000) 1) Min. bunch spacing 200 ns Bunch charge 1 nC Bunch peak current 5 kA Emittance (slice) at undulator 1.4 mm*mrad Energy spread (slice) at undulator 1 MeV

1) The limitation to 3,000 bunches at 20 GeV beam energy is related to a maximum load of 300 kW on each of the beam dumps in the initially installed two electron beam lines.



Overall layout and site3.4km



Schenefeld Site



Schedule

y2007 y2008 y2009 y2010 y2011 y2012 y2013 y2014 y2015

Civil construction

Linac

Accelerator sub-systems

Technical Infrastruct.

Operation & control

Undulator & photon b.l.

1st beam injector1st beam linacSASE1 gain at 0.2nmall beam lines oper.

design, prototyping fabrication (incl. installation commissioning operation & industrialization pre-series) (tech. & beam)



XFEL Cryo Module

BPMs are the only monitor installedIn the 1.2 km long main LINAC

They sit every 12 m at the end of the cavity string together with• Quadrupole• Steerer pair• HOM Absorber



In More Detail

quadrupoleBPMbellows

HOM absorber

gate valveCold BPM with well defined „Interface“• Resolution < 50 µm, single Bunch (RMS) @ 0.3 – 1.2 nC, circular shaped beam• Coupling x/y < 1 %• Particle Free, at least to Class 100 • Beampipe 78 mm, stainless, copper plated• Length 170 mm• „Cavity Fanges2, fixed type on both sides• Fixed directly to the cold quad• Tolerances (Electrical to magnetical axis)

• 300 µm (RMS) Transversal• 3 mrad (RMS) Roll angle



Two Candiates for the Cold BPM

Two Prototypes are installed in TTF, close to each otherDESY Pick up: First Tests with „Neumann Electronics“CEA Reentrant:

– Installed, first RF Tests– Beam Test in the next Accelerator Physics Period of TTF

Pick-up

Reentrant

TTF Installation



Pickup „Prototype“

Needs more Investigation of• Button Size/Geometrie• Feedthrough Technology• Beam Tests have shown Resolution better 50 µm @ 1 nC



First Beam Measurements: 13ACC7 with modified HERA Electronics

• Prototype electronics using the Delay Line Principle

• Peak Detektor sampled with an 81 MHz VME ADC with DOOCS integration

• SB BPM Resolution @ 0.9 nC: 25 µm(measured using correlation techniques)

Q = 0.5 nC

Calc. Steerer Kick

Hor

. Bea

m P

ostio

n

x

y



Reentrant Cavity BPM

Collaboration with CEA Saclay

• Potential of much higher resolution (< 10 µm)• Mechanics more complicated• Cleaning for particle cleanness more problematic.• Possible BPM for ILC ?

Already presented by Claire



Higher Order Modes (HOM) in Accelerating Cavities

other modes: Higher Order Modes (HOM)– excited by the electron beam (unavoidable)– monopole, dipole, quadrupole etc. modes– Need to be damped

Why not use them as Cavity BPMs– All Cavities have HOM Couplers– Potential for sub µm Resolution

Dipole band 1

Dipole band 2

Monopoleband

1.3GHzreference

wakefield spectrum



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Future Cold BPMs at DESY

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