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Reentrant Beam Position Monitors DITANET Topical Workshop on Beam Position Monitors 16 th – 18 th January 2012. Claire Simon. Introduction. Two types of BPMs based on a radiofrequency reentrant cavity are developed :. - PowerPoint PPT Presentation
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16/01/12 DITANET Topical Workshop on Beam Position Monitors
Reentrant Beam Position
Monitors
DITANET Topical Workshop on Beam Position Monitors
16th – 18th January 2012
Claire Simon
16/01/12 DITANET Topical Workshop on Beam Position Monitors
IntroductionTwo types of BPMs based on a radiofrequency reentrant cavity are developed:One monitor is developed for the E-XFEL (Thirsty two of those monitors will be installed in E-XFEL cryomodules) :
aperture of 78 mm designed to work at cryogenic temperature in a clean environment can get a high resolution and the possibility to perform bunch to bunch measurements.
One prototype is installed in a warm part in the Free electron LASer in Hamburg (FLASH), at DESY.. and shown a resolution Resolution measured around 4 µm with 1 nC and dynamic range around ± 5 mm.
The second monitor is developed for the probe beam (CALIFES) of CLIC Test Facility (CTF3) at CERN:
aperture of 18 mm operated in single bunch and multi-bunches modes.
Re-entrant BPM (left) installed on the linac FLASH.
16/01/12 DITANET Topical Workshop on Beam Position Monitors
E-XFEL - Accelerator Complex 17.5 GeV
800 accelerating cavities1.3 GHz / 23.6 MV/m
25 RF stations 5.2 MW each
XFELX-Ray Free-Electron Laser
100 accelerator modules
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Cold BPM (unit cell)XFELX-Ray Free-Electron Laser
100+1 (Injector) Modules along machine with 32 re-entrant BPMs Injector 1M+3rd: Button2x
Linac 1 4M: Button4x(1unit)
Linac 2 12M: 2xReentrant2x(1unit), 2xButton4x(1 unit)
Linac 3 84M: 14x Reentrant2x(1 Unit), 14 x Button 4x (2 Unit)
Schematic from D. Noelle
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Cold Reentrant BPM for the E-XFEL
quadrupole
BPMbellows
HOM absorber
gate valve
XFELX-Ray Free-Electron Laser
Specifications
Single bunch resolution (RMS): 50 µm
Drift over 1 hour: 5 µmMax. resolution range: ± 3 mmReasonable signal range : ± 10 mmLinearity: 10%
Transverse alignment tol. (RMS): 300 µmCharge dependence : 50 µm
Collaboration between DESY, PSI and CEA Saclay
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Design
Arranged around the beam tube and forms a coaxial line which is short circuited at one end. Cavity fabricated with stainless steel as compact as possible :
170 mm length (minimized to satisfy the constraints imposed by the cryomodule) 78 mm aperture.
Eigen modes
F (MHz) Ql (R/Q)l (Ω) at 5 mm
(R/Q)l (Ω) at 10 mm
Measured Measured Calculated Calculated
Monopole mode
1255 23.8 12.9 12.9
Dipole mode
1724 59 0.27 1.15
Twelve holes of 5 mm diameter drilled at the end of the re-entrant part for a more effective cleaning.
Feedthroughs are positioned in the re-entrant part to reduce the magnetic loop coupling and separate the main RF modes (monopole and dipole)
XFELX-Ray Free-Electron Laser
Signal from one pickup
Cu-Be RF contacts welded in the inner cylinder of the cavity to ensure electrical conduction.
Dowel pins to adjust transverse alignment with quadrupole
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Test bench in CryHolab Test in a horizontal cryostat at Saclay (Cryholab)
He tube to cool down
BPM
XFELX-Ray Free-Electron Laser
BPM integrated in CRYHOLAB.
CRYHOLAB.
Frequency (MHz) QlMeasured in Cryholab at
300 K
Estimated at 6 K
Measured in Cryholab
at 6 K
Measured in Cryholab
at 6 KMonopole mode
1254 1257.7 1257.2 22.2
Dipole mode
1720.6 1725.8 1727.7 49
Reflection and transmission measurements
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Feedthroughs
Feedthroughs mounted on BPM body with Conflat gaskets
Brazed ceramic
Manufacturing Process
1. Machining of feedthroughs (carried out by company)
2. Cryogenic test in N2 according to: (carried out by company and by CEA Saclay to check)
3. Transport of feedthroughs to DESY
4. Particle cleaning of feedthroughs
5. RGA and leak test of feedthroughs in clean room (ISO5) at DESY
Cold test procedure for feedthroughs
1. Feedthroughs leak tested
2. Feedthroughs plunged into LN2
3. Operation repeated 3 times
4. Feedthroughs leak tested
XFELX-Ray Free-Electron Laser
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Process steps for the reentrant cavity BPM (1)
XFELX-Ray Free-Electron Laser
1. Firing at 950°C and machining body (carried out by company)
2. Copper coating (acid bath) of 2 parts (carried out by company). Using of tools to protect reentrant part and outside parts which are not copper coated.
Ultrasonic bath + Heat treatment 300°C for 1 h + visual check Thickness measurement 12 µm ± 2 µm with 1 µm of Nickel to do the contact between stainless steel and copper
3. Welding of RF contacts and EB welding of 2 parts composing the BPM (carried out by company)
4. Cleaning, leak test and RGA (carried out by CEA/Saclay) Cleaning in US bath Leak test: leak rate must be <= 1*10-10 mbar l /s Residual gas analyze : sum of residual gases with mass < 45 not exceed 10-3 of total pressure which is ≤ 10-8 mbar
5. Process in clean room ISO5 (carried out by DESY) Particle Cleaning, Residual gas analyze, Transport to ISO3
6. Process in clean room ISO3 (carried out by DESY) Assembly of quad and BPM High pressure rinsing of quad-BPM assembly Assembly feedthroughs and checking Assembly of quad-BPM unit with valve and pump tube with valve Leak check and RGA spectrum total unit Packing and Transport to Saclay
BPM Mounting in an XFEL prototype cryomodule
16/01/12 DITANET Topical Workshop on Beam Position MonitorsFrame of re-entrant RFFE electronics
First RFFE prototype installed
First RFFE electronics prototype designed with a reference frequency of 9.028 MHz installed at FLASH
Digital electronics 8-channel Fast ADC with 14 bits resolution used.
XFELX-Ray Free-Electron Laser
BPMs in the linac tunnel
beam positionmonitor
x1
x2
y2
y1
180°hybrid
3 dBcombiner
x
y
Qx
ADC
Digital board
Ix
Qx
Iy
Qy
180°
hybrid
Ix
Qy
Iy
Low passFilter 70 MHz
Low passFilter 70 MHz
PLL
reference10 MHz1 Vpp
RF front-end
Band pass filter1724 MHz
110 MHz BW
Amplifier
Isolator
Detector
Isolator
LO
RF
LO
RF
90°hybrid
LO
RF
LO
RF
90°hybrid
Mixer
Mixer
3 dBsplitter
3 dBsplitter
3 dBsplitter
Phaseshifter
VideoAmplifier
Attenuator
Attenuator
control unitTo pilot
attenuators, switchs
PLL
3 dBsplitter
Attenuator
reference10 MHz1 Vpp
3 dBsplitter
Band pass filter1724 MHz
110 MHz BW
Band pass filter1250 MHz
110 MHz BW20 dBm leak.
20 dBm leak.
9.028 MHz
9.028 MHz
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Calibration results from horizontal (left) and vertical (right) steering at 0.5 nC
XFELX-Ray Free-Electron Laser
Good linearity in a range ± 3 mm
RMS resolution ~ 10 µm on Y channel with beam jitter
~ 48 µm on X channel with beam jitter
Beam measurements with first RFFE prototype
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Cavity BPM Hardware Concept
2 Reentrant Cavity RF front-ends, GPAC as digital back-end.
P2
RFFE2
P2
8 x MGT
P0
P0
Power GPACSFP/Trigger RFFE1
8 User IO2 Ctrl IO4 Trig IO
23 Special
Front EndBack End
2 SMB2 IPMB
3 Special P2
RFFE3
P2 P2
P2
User [32:47]
User [48:63]
Hot Swap Signals
P0 ADC
Ho
t S
wap
User [0:15]
User [16:31]
RFFE4
216.667 MHz
6 ch 160 MSa/s ADC GPACReentrant RFFEReentrant
Cavity
63 6 x 16 bit
160 MHz
ADC samples
I2C
MBU Backplane
6 ch 160 MSa/s ADC
Reentrant RFFE
63 6 x 16 bit
160 MHz
ADC samples
I2C
ReentrantCavity
Machine RF
160 MHz
160 MHz
By Courtesy of Raphael Baldinger, Goran MarinkovicMore information, please see E-XFEL/SwissFEL BPMElectronics‘ talk
PAUL SCHERRER INSTITUT
XFELX-Ray Free-Electron Laser
16/01/12 DITANET Topical Workshop on Beam Position Monitors
XFELX-Ray Free-Electron Laser
Second RFFE prototype
Option: for charge < 0.1 nC
16/01/12 DITANET Topical Workshop on Beam Position Monitors
E-XFEL infra- structure requirement: spacing will be N*111ns, with N=integer and >=2
Reference frequency : 216 MHz and then adding of a frequency divider to get 9 MHz
Adding of crystal oscillator on PCB board in backup if reference signal 216 MHz fails
Give a flag, showing something is wrong with the 216 MHz No exact value of the position – error position high
New design of sum channel with band pass filter at the dipole mode frequency and IQ demodulation Normalize position signal to reference (amplitude and phase) if small beam time arrival moved can be determined.
change of phase can be determined
Adding of ADC clock (design from M. Stadler/PSI)
Adding of Hot Swap control design with new components (design from R. Kramert and R. Baldinger/PSI)
Interfaces: “Two I2C buses” to control all RFFE functions
Differential outputs integrated on PCB board
Option 2 charge ranges: low charge (from 100 pC to 20 pC) adding switches, variable attenuator and amplifier on X and Y channels
Evolution of the second prototype
XFELX-Ray Free-Electron Laser
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Damping time is given by using the following formula :
Time Resolution
BW*
1
ldQ
df
BW
Damping Time cavity only
Time resolutioncavity + electronics
BPM 9.4 ns 40 ns
With fd: dipole mode frequencyQld: loaded quality factor for the dipole mode
Considering the system (cavity + signal processing), the time resolution is determined, since the rising time to 95% of a cavity response corresponds to 3τ.
Time resolution for re-entrant BPM
RF signal measured at one pickup
ΔT =1µs
100 bunches read by the re-entrant BPM
20 ns
20 mV
40 ns
IF signal behind Lowpass Filter on
channel Δ
XFELX-Ray Free-Electron Laser
16/01/12 DITANET Topical Workshop on Beam Position Monitors
CALIFES linac – Probe Beam of CTF3
6 BPMs are installed on the CALIFES linac
15 MV/mcompression
17 MV/macceleration
17 MV/macceleration
LIL sections
beam dump
Focusing coils
K
quadrupoles
LaserRF pulse compression
2 x 45 MW
10202525
Profile monitor
Beam position monitor
Steerer
RF gun cavitySpect. magnet RF deflector
Bunch charge (single/multi bunch): 0.6 nC/ 6 nC/NbBunch length (rms) : 0.75psInitial /final bunch spacing :5.3/1.8 ps, 1.6/0.5 mmTrain length: 21 - 150 nsTrain spacing (rep. rate): 5 Hz
SpecificationsEnergy ~ 170 MeVEmittance < 20 .mm.mradCharge per bunch : 0.6 nCEnergy spread: <2%Number of bunches : 1- 32 – 226
Collaboration between CERN and CEA Saclay
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Reentrant Part
Reentrant Cavity BPM for CALIFES
Bent coaxial cylinder designed to have:
a large frequency separation between monopole and dipole modes
a low loop exposure to the electric fields
Cavity fabricated with titanium and as compact as possible : ~125 mm length and 18 mm aperture 4 mm gap
BPM
16/01/12 DITANET Topical Workshop on Beam Position Monitors
E field
H field
RF Characteristics
With Matlab and the HFSS calculator, we computed R/Q Ratio.
and k=w/c R: the Shunt impedance and Q: the quality factor
Wf
V
Q
R
***2
²
dzezEV jkz*)(
Due to machining, dipole mode frequencies are different for each BPMs.
Standard deviation on the dipole mode: ~ 10 MHz
Eigen modes
F (MHz) Ql (R/Q) (Ω) (R/Q) (Ω)
Calculatedwith HFSS
in eigen mode
Measured in the CLEX
Calculatedwith HFSS
in eigen mode
Measuredin the CLEX
CalculatedOffset 5
mm
CalculatedOffset 10
mm
Monopole mode
3991 3988 24 26.76 22.3 22.2
Dipole mode
5985 5983 43 50.21 1.1 7
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Signal Processing for CALIFES BPM
Hybrids installed close to BPMs in the CLEX
Multiport switches used to have one signal processing electronics to control six BPMs.
Analog electronics with several steps to reject the monopole mode
BPMs in the probe beam linac tunnel
beam positionmonitor 1
x1
x2
y2
y1
180°hybrid
180°
hybrid
phaseshifter
3 dBcombiner
beam positionmonitor 6
x1
x2
y2
y1
180°hybrid
180°
hybrid
3 dBcombiner
.
.
.
6 to 1multiportswitch
phaseshifter
x
y
6 dB
6 dB
18 dBm leak.
18 dBm leak.
Filter 5997 MHz600 MHz BW
0 to 70 dB
0 to 70 dB
18 dBm leak.
Lowpass Filter120 MHz
0 to 70 dB
3 dBsplitter
reference2.891 GHz
14 dBm
RF electronics in the hall
8channel
videoamp
Gv = 10
4channel10 bits2 Gs/sADC
2channel10 bits2 Gs/sADC
DAQ in the hall
control unit
VME Crate
signals for switchesand variable
attenuators control
Ix
Qx
Iy
Qy
Filter 5997 MHz600 MHz BW
RF
LO
II-Q
demodulator
Q
RF
LO
II-Q
demodulator
Q
Lowpass Filter200 MHz
Filter 3990 MHz400 MHz BW
AcqirisDigitizers
Hybrid
couplers
RF electronics used synchronous detection with an I/Q
demodulator.
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Beam tests To calibrate the BPM:
Beam is moved with one steerer.
Calculate for each steerer setting, the relative beam position in using a transfer matrix between steerer and BPM (magnets switched off to reduce errors and simplify calculation).
Average of 15 points for each steerer setting.
Good linearity in a range ± 1.5 mm
RMS resolution: ~58 µm on the Y channel with beam jitter
~98 µm on the X channel with beam jitter
Calibration results from horizontal (left) and vertical (right) steering
16/01/12 DITANET Topical Workshop on Beam Position Monitors
Summary
E-XFEL reentrant BPM: Mechanics (BPM body/Cavity + feedthroughs) under construction Second RFFE prototype under construction Tests at FLASH going on
CALIFES re-entrant BPM: In using with beam
Special thanks to CERN, DESY, PSI and CEA/Saclay Colleagues for their collaboration to CALIFES and E-XFEL reentant BPMs
Thank you for your attention