1. Status and plans for the 3.9 GHz section of XFEL
Redefine “Large Production” here
1 Module
8 Cavities
Paolo Pierini, INFN

2. Based on FNAL FLASH ACC39 developments
XFEL 3° Harmonic System
3.9 GHz RF system is right after injector module, before first bunch compressor
Based on FNAL FLASH ACC39 developments
Max 40 MV required in a 8 cavity module
Gradients are well within achieved FNAL cavity/module performances
cavity active length m
i.e. standard BCP treatment is sufficient for performance
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

3. XFEL Cavity string layout: Coupler kicks
M. Dohlus, DESY
Analysis of coupler kicks: one string configuration leads to compensation of offset independent kicks
every 2° cavity rotated around longitudinal axis
Used in XFEL String
Quad at module entrance
control both planes
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

4. Status of cavity components
Mockups + 3 Cavity prototypes
To develop fabrication/processing capabilities
starting from FNAL experience
RF design unaltered
small variations (flanges/cones, ...)
Built, tuned, BCP treated since mid 2009
Waiting testing capabilities in LASA since then... 
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

5. Tuning BCP etching parameters with Nb mockup
A factor of 2 between iris and equator material removal accounts for the change of frequencies and coupling
Before etch
After etch
Slater perturbation on the single cell profile that reproduces the 240 um average material removal suggests 180 um at equator and 355 um at iris, factor of 2 confirmed
5.3 MHz/100 um average rate, after optimizing pump pressure
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

6. Field Flatness tuning after fabrication
FF (>90%)
within 1 mm length
After fabrication (and 800°C)
Frequencies (no fms wire)
Frequency MHZ
Length mm
3HZ01
(+0.7)
3HZ02
(+0.9)
3HZ03
(+0.4)
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

7. Main etch of 3HZ502: Etching Sheet
Three treatments with RF monitoring, for an average removal of 137 um (goal was 3x50 um=150 um)
Confirmed etch rate -5.3 MHz/100 um
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

8. Existing 500-700 MHz Vertical Test Facility Cryogenic refurbishment
VT area LASA
Existing MHz Vertical Test Facility
Cryogenic refurbishment
18 2 K / K
less than 1 W in static conditions
Adapted VT insert to 1.3 GHz single cells and 3.9 GHz cavities
New RF hardware
100 W at 1.3 GHz
200 W at 3.9 GHz
Still, clean room, UPW plant and HPR to be qualified for operation
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

9. Qualification of test stand /1
One single cell, 1.3 GHz cavity (1DE15) has been prepared by DESY, to re-measure in LASA, for calibration purposes
“as-received”, without opening it, for the VT debugging
Eaccmax = 34.7 MV/m
Eaccmax =
Test at LASA
Eaccmax = 38 MV/m
Eaccmax =
 Completed
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

10. Qualification of test stand /2
The next stage, in the following weeks, is to re-assemble cavity 1DE15 in the clean handling area in Milano, verifying all needed tooling and training people
Enter in clean room
Dismount antennas
Perform HPR, dry under laminar flow
Reassemble everything
Mount on VT and re-test
When second test gives similar results than obtained from the cavity “as-received”, we can start testing the 3.9 GHz cavities
Expect 3.9 GHz results by spring
 Ongoing
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

11. Dressed cavity package(s)
Due to alternating couplers requirement and to the position of the 2-phase pipe there are two dressed cavity configurations (left and right)
Blade tuner is of the “slim” type, concept derived from all ILC tuner work. Lighter, motor to the side.
Beam direction
ZROT
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

12. XFEL Cryomodule: transverse layout
Design is “Plug compatible” with Type III+/XFEL modules
Identical transverse X-section for all cryo piping
Adapts at longitudinal interfaces of standard cryo components
Shorter module and string lengths
Module part of the same cryo line with the injector module
All cryo piping in the same relative position with respect to beam axis
Cavity package and support to HeGRP are different
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

13. Longitudinal interfaces preserved
XFEL 1.3 GHz
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011

14. Schedule for XFEL 3H cavity/module activities
Test prototypes in VT
spring 2011
Procurement of prototype He Vessels and Tuners for the three structures
start horizontal tests of prototypes
Launch the cavity procurement (including tanks)
summer 2011
Complete the module design and launch procurement
end 2011
P. Pierini, TTC Meeting, Milano, 28/2-3/3 2011