1. Vibrational Stability of a Cryocooled Horizontal-Bounce Double Crystal Monochromator
MEDSI 2016
Paw Kristiansen
13 Sep 2016

2. If this vertical vibration is too much
Two years ago in Melbourne…
A vibrational number is pointless without a physical frequency range.
Relative pitch level of DCM 48 nrad RMS, Hz
(and 17 nrad RMS over 2 – 100 Hz)
If this vertical vibration is too much
Horizontal DCM
48 nrad RMS, Hz and 17 nrad RMS in the Hz region
Difreation limited rings where the vertical and hororizontal vibrational requirements are about the same
one solution

3. HDCM functionality Energy range Si111: 5 – 30 keV
Constant horizontal offset: 10 mm
Go through each stage stage – say that the 1st crystal is indirectly side cooled and the 2nd is braid cooled.

4. HDCM, NanoMAX at MAX IV

5. HDCM internal
Spend some time on the flow path of the LN

6. Measurement setup NXC NanoSensor from Queensgate, 0.1 nm at 5000 Hz
Directional stability…
So this is a direct measurement!!!

7. Measurement setup

8. Relative pitch vibration
Talk about the standeviations.
Talk about 5.9 bar. The cryocooler model used, the E-series…
And mention that 5 Hz equals ca. 1 L/min
Baber liconson

9. Available cooling power
V is flow rate, ρ is density, C is heat capacity and TPot is the difference in temperature between the LN2 sacrificial cooling bath of the cryocooler, 77 K, and the boiling temperature of the circulating LN2, e.g. 18 K at 5.9.
Need a common axis -> available cooling power.
3 L/min -> bar
4 L/min -> bar
Not suggesting to put in 1500 W!

10. Two trends: Lower flow -> lower vibration and lower standard diviation (the last not so obivious)
Six measurements over the full bragg

11. 120 nrad RMS at 10.15° (11.22 keV) 7 meV RMS offset change 0.2 nm RMS.
Only at one angle ! (10 deg )
120 nrad RMS at 10.15, corresponding to the K Se fluorescence energy at keV on the Si 111 crystals, leads to an energy jitter of 7 meV RMS off the first crystal and a beam offset change of 0.2 nm RMS.

12. Relative vs absolute vibrations
Appsolute appears in a area where where they will be picked up by the relative…

13. Internal cryo support – absolute vibration

14. Note displavement – not angle!
Up to 350 Hz
to 350 Hz

16. Conclusions
Relative horizontal pitch stability 25 nrad RMS, 1 – 2500 Hz, at Epot = 1500 W
More rigidity is not always better – frequency band considerations needed
Lowering the flow rate reduces vibration  higher pressures needed…
Outlook
Re-design/dimensioning of the in-vacuum LN flow path
Higher pressure of the circulating LN

17. Will there be enough flow..?
500 W → 1.2 L/min at 12 bar → Re = 3380
h = 1640 W/(m2 C)
Temperature rise across the boundary layer = 27 K

18. Questions ?
Stand 10

19. Interferometer low Hz limited