The TESLA XFEL Project by dfhdhdhdhjr

VIEWS: 4 PAGES: 26

									 DESY meeting with KEK ILC Delegation (March 7th 2005)


                TTF / VUV-FEL Status
                               and
             Some Words of Fast Kickers
                        Hans Weise / DESY




Hans Weise                                               DESY / 07.03.2005
         TESLA Test Facility Linac – Phase II
FEL User Facility in the nm Wavelength Range (VUV) and
                     R&D for the ILC

RF gun               accelerator modules        collimator   undulators



                  bunch             bunch                                                FEL
Laser           compressor        compressor                        bypass
                                                                                     experimental
   4 MeV        150 MeV           450 MeV      1000 MeV                                  area




   Hans Weise                                                                DESY / 07.03.2005
     TTF / VUV-FEL Status as of January 13th, 2005
The VUV-FEL Set-up:
• installation completed until end of 2004
    • includes        RF gun
                      five accelerator modules
                      two bunch compressors
                      electron beam collimation
                      electron and photon beam diagnostics
                      undulator section

• still missing are
    • the 3.9 GHz rf system at the end of the first accelerator module
      (needed for short wavelength FEL operation, scheduled for 2006)
    • some electron beam diagnostics, esp. beam position monitors
    • sixth accelerator module to increase the electron beam energy to 1 GeV
    • the photon beam transport to the user‘s experimental hall
    • the user‘s photon beam lines (to be commissioned until 5/2005)
  Hans Weise                                                      DESY / 07.03.2005
        VUV-FEL Status as of January 13th, 2005
Electron beam commissioning done with single bunches per bunch train
Measured beam emittance (90%) at 120 MeV (BC2 section) is 1.3 pi mm
  mrad in both planes without compression at 0.5 nC; compression slightly
  decreases beam quality (as expected) but the beam quality seems to be
  good enough for lasing at 30 nm; shorter wavelengths need 3.9 GHz
  system in order to keep the emittance small.
Chosen beam energy is 450 MeV, thus corresponding to 30 nm
First spontaneous spectrum was taken in 12/2004




At present beam based alignment is used to find the correct electron
   beam orbit inside the undulator, i.e. first lasing should happen soon.
Hans Weise                                                      DESY / 07.03.2005
             VUV-FEL Status as of January 14th, 2005
 First lasing established on January 14th!!!                 • We now have six weeks of SASE operation
average bunch charge 0.6 nC                                  • Photon pulse energy increased to typ. 5 µJ
 first accel.module ACC1 approx 6 deg off-crest                (a factor 2 below saturation)
 electron beam energy at BC2 set for 125 MeV
 accel.modules ACC2/3 on-crest (within 1-2 degrees) accel.   • Photon beam parameters measured with
                                                               excellent agreement to theoretical predictions
 BC3 (bunch compressor) on with currents set for 380 MeV
 beam energy in undulator 450 MeV                            • Stable FEL operation over typ. 15 minutes; then
 undulator optic: FOFO and all undulator correctors off,       slight tuning necessary
 quadrupole movers have not been activated.
                                                             • 90% emittance of compressed bunches approx.
FEL gain: 1E5 (saturation would correspond to 1E7)             1.6 mm mrad in both planes
 Photon pulse energy    ~1 micro-Joule
 Photons per pulse      5E11                                 • some control loops established in order to
                         photons/sec*mm2*mrad2*0.1BW           stabilize SASE
                                                             • still some trouble with the beam orbit inside
                                                               the undulator

                                                             At present some shut-down activities
                                                             • connect undulator beamline with user‘s photon
                                                               beam lines
                                                             • modify interlock system
                                                             Restart on March 21st.




    Hans Weise                                                                              DESY / 07.03.2005
                    VUV-FEL Setup / Overall Layout


RF gun               accelerator modules        collimator   undulators



                  bunch             bunch                                                FEL
Laser           compressor        compressor                        bypass
                                                                                     experimental
   4 MeV        150 MeV           450 MeV      1000 MeV                                  area




    accelerator modules                                       undulator section

   Hans Weise                                                                DESY / 07.03.2005
 TTF / VUV-FEL as Prototype for the XFEL Injector

                                       σz = 2.0 mm       112 µm         22 µm
RF Gun   s.c. Acc.
                        3rd harm.   s.c. Booster Linac    Bunch Compressor      Main Linac
                        Structure




                     100 MeV                                      500 MeV

The goals for the XFEL:
charge           1nC
x,y             1.4 µm
z               ~ 20 µm (80 fs)
E, uncorr                     < 2.5
MeV


At TTF and PITZ (DESY)
we are already close to
these parameters.
Hans Weise                                                                        DESY / 07.03.2005
                   TTF2 / VUV-FEL Tunnel Layout


The TTF2 Tunnel
installation basically
follows the old TESLA
design…
With all its advantages
and disadvantages.




Hans Weise                                        DESY / 07.03.2005
      TTF2 Installation / Warm Beam Line Sections




Hans Weise                                  DESY / 07.03.2005
                            XFEL Linac Tunnel Layout

Accelerator is housed in a 5.2 m diameter tunnel ~ 15 - 30
m underground.
Klystrons in tunnel are connected to modulators in an external
hall by 10kV pulse cables.
Preferred installation concept is suspension from tunnel ceiling

   accelerator
     module


                                klystron




                 RF pulse
                  cable



Hans Weise                                              DESY / 07.03.2005
                     RF Unit of the XFEL (32 cavities)



                       var. Q_ext
                            with
                        adjustable
                         coupler
                          and/or
                                        5 MW RF
                        waveguide
                           tuner         source      De-rated    Bouncer-type
                                                    10MW MBK      modulator



             Acc 1              Acc 2             Acc 3         Acc 4


         eight 9-cell Nb
         cavities at 2K,
             Q0=1010

                                            12m TTF-
                                            like acc.
                                             modules



Hans Weise                                                          DESY / 07.03.2005
                          RF Operation of s.c. Cavities

       vector                               TTF RF Unit
      modulator MBK Klystron      1 klystron for 2 accelerating modules
                                         8 nine-cell cavities each



                                     circulator
               DAC
         DAC




                                                                             Mechanical tuner
                                                                             (frequency adj.)
                                     stub tuner (phase & Qext)
         Low
         Level
                                     coaxial coupler
          RF
        System



                                         cavity #1                           cavity #8

                                                                                  pickup signal
                     vector sum
                                                  ADC

                                                  ADC                 accelerator module 1 of 2
                                                          vector
                                                        demodulator

Hans Weise                                                                        DESY / 07.03.2005
           RF Operation of Accelerator Modules
        Above its Performance Limit (e.g. Module 1*)
 Cavity quench detection algorithms and
 exeption handling procedures analyze the probe
 signals...




Stable Module #1* operation with slowly but steadily increased gradient

  1st quench: Cavity 2              2nd quench: Cavity 6              3rd quench: Cavity 1
      Eacc=19 MV/m                      Eacc=21 MV/m                      Eacc=24 MV/m


Hans Weise                                                                        DESY / 07.03.2005
          RF Operation of Accelerator Modules
       Above its Performance Limit (e.g. Module 1*)

                                 The maximum operating gradient of s.c. cavities
                                 • is set by cavity quench, field emission, or
                                   Q-degradation – not by structure breakdown
                                 • is not a hard limit. A too high gradient results in increased
                                   cryogenic load, radiation, and dark current
                                 • does not trip off cavities in ns but in typ. 100 µs
                                   if cavities are operated at the threshold
                                 An exception handler as part of the LLRF can avoid quenches.
                                 • Action can be taken prior to the next pulse.
                                 • Consequences for the machine safety are very positive,
                                   i.e. correctly injected bunches will not be lost in the linac.

In a high gradient long pulse run in spring 2002, an accelerator module was operated with stable
beam (5 mA, 800 µs) close to its gradient limit.
The acc. module was operated with a typ. module on-time of 90% at increasing gradients:
                    39 days at 19.5 MV/m, 800 µs, 5 Hz
                     4 days at 20.0 MV/m, 800 µs, 1 Hz  1 Hz operation due to beam oper.
                     6 days at 21.5 MV/m, 800 µs, 1 Hz  laser + gun were limited



Hans Weise                                                                               DESY / 07.03.2005
               TTF Cavities above 25 MV/m Gradient




                                                               Cav.5 @ ACC1 was
                                                               electropolished and
                                                               reaches 35 MV/m flat top
                                                               after module installation
                                                40


                                                35


                                                30


                                                25


                                   Eacc[MV/m]   20



10 out of 16 cavities in                        15



modules ACC4 / ACC5 can be                      10



operated flat top at approx.                    5



29 MV/m                                         0
                                                     0   500       1000            1500     2000       2500

                                                                          t [ms]


  Hans Weise                                                                       DESY / 07.03.2005
                           Dark Current Measurement
The on-axis dark current was measured for modules ACC4 /          Dark Current vs. RF phase with
ACC5.                                                             respect to neighbouring cavities
                                                                  is just as expected
Only one cavity in module ACC5 produced a mentionable
dark current.                                                          (max        min) over pi/2
• captured dark current could be
  measured at the exit of ACC5
• there was no d.c. from this cavity
  at the entrance of ACC4
• the d.c. decreased as a function of time
 after module commissioning (August 2003)
          100 nA at 16 MV/m increasing by a
          factor 10 for each 4.4 MV/m gradient step
          i.e. approx. 10 µA at 25 MV/m
 May 4th
           100 nA at 20 MV/m increasing by a
           factor 10 for each 3.7 MV/m gradient step,
                                                                  Reminder:
           i.e. 1.2 µA at 25 MV/m
                                                                  The TESLA limit is defined by
 September 22nd
                                                                  additional cryogenic losses:
        after a few weeks on-time at 20 – 25 MV/m
        250 nA at 25 MV/m                                             The captured d.c. has to stay
• detuning of cavity no. 6 left over an integrated dark current       below 50 nA per cavity.
  of the order of 20 to 25 nA at 25 MV/m average gradient             (see TESLA Report 2003-10).

  Hans Weise                                                                        DESY / 07.03.2005
                   TTF2 / VUV-FEL Beam Commissioning
                                    •   re-commissioning of gun + injector
                                    •   setup cavity phases ACC2-5  beam energy
         1st beam
                                    •   setup bunch compression
         (bypass)
                                    •   setup beam linear optics, optimize orbit
                                    •   commissioning of diagnostics




                                                                 First measurement              after
                                                                 before adjustment           adjustment




•   re-commissioning of gun + injector         done
•   setup cavity phases ACC2-5  beam energy   done
•   setup bunch compression                    done
•   setup beam linear optics, optimize orbit   on-going
•   commissioning of diagnostics               on-going
    Hans Weise                                                                       DESY / 07.03.2005
                     TTF2 / VUV-FEL Beam Commissioning

                                               •   setup collimation
                FEL 30 nm                      •   emittance measurements and optics matching
                1 bunch                        •   beam-based alignment in undulator section
                                               •   commiss. of photon diag. with spon. emission

                                                             Beam




     Ion pump
                      wirescanner



quadrupole

                              stretched wire
                                 position
                              control system

                                granite
                                baseplate
   beam




                                                                                         MCP Diagn.

                                                                                   A. Fateev et al., Dubna
     Hans Weise                                                                            DESY / 07.03.2005
             TTF2 / VUV-FEL Beam Commissioning

                     •   commissioning of FEL diagnostics
     Saturation
     & 6-100 nm      •   study of FEL beam, compression schemes, etc.
                     •   establish reproducible settings, etc.

                     photon
                   diagnostics      gas absorber     photon diagnostics




                                                         beam
                                                         dump



                   FEL hall         PETRA tunnel          LINAC tunnel

Hans Weise                                                   DESY / 07.03.2005
                                                             TTF2 / VUV-FEL Outlook
    Long time operation of all 5 acc. Modules.
    VUV-FEL Commissioning.
    First lasing achieved.
    Stable operation / saturation spring 2005.
    Start user operation in spring 2005

    Accelerator Module ACC6 with electro-polished
    cavities should first be tested in a separate test
    stand. Schedule: a.s.a.p., but not before end of
    2005.
0




1.0E+11 1
      10
                               1
     Unloaded Quality Factor




                                            Electro-polished Cavities
                                            Measured in Vertical Test



1.0E+10 1
      10
                               0
                                                         AC70    AC72
                                                         AC73    AC78
                                                         AC76
1.0E+09 9
      10
                                   0       10          20          30      40
                                   0      10           20          30
                                          Accelerating Gradient (MV/m)     40
                                       Accelerating Gradient Eacc [MV/m]



                       Hans Weise                                                     DESY / 07.03.2005
             VUV-FEL Program for 2005




                          The 2005 operation time is
                          divided in different blocks.
                          Under the assumption of no
                          unexpected shut downs, all
                          requests can be full-filled.
                          Some reserve is within the
                          individual operation periods.




Hans Weise                                         DESY / 07.03.2005
                A Fast Pulser for a Fast ATF Kicker




                             The actually used pulser ready for the
                             connection to a fast kicker or the ATF
                             kicker




 Hans Weise
Frank Obier & (Hans Weise)                                            DESY / 07.03.2005
                      Stripline used for pulser tests
                             Test kicker (stripline in vacuum);
                             matching not optimized
                             1.5 m cable RG213 between pulser and
                             kicker
                             • reflection at both stripline ends (right
                             plot)
                             • and some ringing as a consequence of
                             the reflection (left plot)




 Hans Weise
Frank Obier & (Hans Weise)                                                DESY / 07.03.2005
                                     The 10 ns Switch
                                                        10 ns switch   6.5 kV    70 A
                                                        All pictures show the same signal but have
                                                        different scaling in order to look at ripple
                                                        and ringing.
     Schalter HTS 80-12UF ton=10ns




 Hans Weise
Frank Obier & (Hans Weise)                                                DESY / 07.03.2005
                         Ringing at the end of the pulse.
                                                                     Same pulse, different scaling (zoom)
                                                                     Picture shows ringing at almost acceptable
                                                                     amplitude.
               Schalter HTS 80-12UF ton=10ns




                                                      3,7 %




                                                              6,8‰



                                               40ns




 Hans Weise
Frank Obier & (Hans Weise)                                                             DESY / 07.03.2005
    Schalter HTS 80-12UF ton=10ns   And now a ceramic kicker…




 Hans Weise
Frank Obier & (Hans Weise)                                      DESY / 07.03.2005

								
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