BEAMLINES SOPHISTICATED SYSTEMS CONSTRUCTED FROM SIMPLE BUILDING BLOCKS An introduction to beamline engineering. Author - Title (Footer) 2

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2 BEAMLINES SOPHISTICATED SYSTEMS CONSTRUCTED FROM SIMPLE BUILDING BLOCKS An introduction to beamline engineering Author - Title (Footer) 2

3 BEAMLINES SOPHISTICATED SYSTEMS CONSTRUCTED FROM SIMPLE BUILDING BLOCKS An introduction to beamline engineering Outline What are we dealing with? Basic beamline functions and generic solutions. Heatload Management Vacuum Supports Positioning Author - Title (Footer) 3

4 What comes out of the Front End (looking towards the machine) Radiation from Dipole magnet downstream of straight section Undulator beam Radiation from Dipole magnet upstream of straight section Author - Title (Footer) 4

5 What is delivered to the beamline (high power front end) Aperture in Front End defining the beam. 4mm diameter diamond window Author - Title (Footer) 5

6 Power frofile for a single u27 at the primary slits Author - Title (Footer) 6

7 Laser welder 8 KW can welder metal tubes seams at 60m/min Power Comparisons New upgrade beamlines UPBL11 8 metres of undulator u27 gap 1mm gives max power density 385 Watts/mm2 Total power through the Front End approx 4 kwatts Author - Title (Footer) 7

8 Outline What are we dealing with? Basic beamline functions and generic solutions. Heatload Management Vacuum Supports Positioning How do we process these beams? Slits/Absorbers Windows Optics Author - Title (Footer) 8

9 How do we process these beams? Slits 4 Independent blades each capable of intersecting the entire beam. Power in Q Fluid temperature Proportional to flow rate and Q Maximum temperature Proportional to k thermal conductivity Proportional to Q Dependant on geometry Wall temperature Dependant on exchange coefficient (Flowrate) Choose Copper (high thermal conductivity) Water cooling (turbulent flow) Author - Title (Footer) 9

10 How can this fail? Simple approach: The surface should not melt! More conservative approach: The thermal induced stress should not exceed 2 x thermal yield strength of the material. Choice of Glidcop a dispersion strengthened copper which maintains high yield stress even after brazing Choice of material Melting temp o C Conductivity W/mK Diamond Copper Aluminium Stainless Steel With optimized cooling geometry gives a maximum power absorption of 50W/mm length of absorber Author - Title (Footer) 10

11 Initial Primary Slit design q Q W/mm z Why was it so big? Present High Power Slits y Power absrbed per mm of absorber = Qsinq If we have power densities of 1000 W/mm then q should be less than 2.8 degrees z y Grazing angle 1.8 degrees Author - Title (Footer) 11

12 How do we process these beams? WINDOWS Window, attenuators and CRLs can be treated the same. h t In the central zone this can be approximated to a 1 dimensional problem Assuming copper at constant temperature (20C) Q absorbed = -kadt/dx Q abs/mm = k x t x DT x 2/h DT = h Q abs/mm /2kt Materials and thicknesses Example a.0.3mm diamond in u27@11mm absorbs 28W/mm if h =6mm then temperature = 140 o C Example b 0.3mm aluminum in u27@11mm absorbs 41W/mm if h =6mm then temperature = 1180oC Author - Title (Footer) 12

13 In real conditions Beam is not linear approx 3mm horizontally x 1mm vertically. Copper cooling block is not constant temperature Material is not isotropic HP attenuators Author - Title (Footer) 13

14 Typical attenuator foils that are now used CVD diamond Pyrocarbon Pure aluminium CVD diamond coated with high z material Not to forget our initial problem! Author - Title (Footer) 14

15 How do we process these beams? OPTICS Monochromators Mirrors The difference: size of the projected beam on the optical surface. Monochromator Mirror Angle of incidence (Bragg Angle) 4-70 degrees Typical Footprint 3mm x 3mm Power density up to 100 W/mm2 Total power up to 300W Angle of incidence (Bragg Angle) 0.1 to 0.3 degrees Typical Footprint 3mm x 500mm Power density up to 1 W/mm2 Total power up to 800W Author - Title (Footer) 15

16 How do we process these beams? OPTICS Mirrors Mirror cooled by In/Ga baths. In/Ga is a safe mercury. Liquid metal for good flexible thermal contact Author - Title (Footer) 16

17 deformation (m) temperature deg C Results How do we process these beams? OPTICS temperature along mirror mA 160mA 160mA width corr Secondary slit Primary Slits distance along mirror (mm) If the mirror is inserted in the white beam part will be reflected and part will be absorbed. The absorbed beam will heat up the surface of the mirror and also the bulk of the mirror. The temperature of the surface can be calculated and varies according to above graph. It will vary with different currents in the machine.. From these temperatures the deformation of the surface can be calculated and corrected using a bender. 4.50E E E E E E E E E E+00 Deformation of mirror distance along mirror End effect outside useful beam 200mA corrected 200mA 160mA 160mA corrrected 200mA 160mA width corr 160mA width corr 200mA Author - Title (Footer) 17

18 The New ESRF Generic Mirror Solutions Final choice for ESRF ID24_MH1 Specific horizontally deflecting mirrors ID24 Smart section mirrors Water cooling on top of side Clamps for cooling absorbers and Indium foil interface T Mairs et al Upgrading Beamline Performance : Ultra Stable Mirror Developments at ESRF 18

19 Monochromators How do we process these beams? OPTICS Optimised cooling as seen before. Author - Title (Footer) 19

20 Monochromators Why liquid nitrogen Thermal conductivity (w/mk) vs temperature Aim is to keep this region as flat as possible temperature (K) Author - Title (Footer) 20

21 But we still have After the monochromator the heatload problem disappears PHEW! Outline What are we dealing with? Basic beamline functions and generic solutions. Heatload Management Vacuum Supports Positioning Author - Title (Footer) 21

22 VACUUM Vacuum is not the specialisation of the mechanical engineers working on beamlines, but vacuum chambers are used everywhere. Some figures: ESRF subsystem length vacuum chambers vacuum level Booster 300 metres 10-8 mbar Storage Ring 32 cells x 26m =844 metres mbar Front Ends 47 x 20m = 940 metres 10-9 mbar Beamlines 47 x m = metres mbar Vacuum Regimes Rough Vacuum: Atm (1000mbar) mbar Process Vacuum: 10-2mbar mbar High Vacuum: 10-5mbar mbar Ultra-High Vacuum: < 10-9mbar Generally beamlines operate in the high vacuum region. But why? Author - Title (Footer) 22

23 Beamline Vacuum requirements Maximum transmission of photons Vacuum level transmission for 1 metre at energy mbar 2keV 4.5keV 7keV 12keV 20keV % 0.5% 25% 76% 93% % 59% 87% 97% 99% 10 55% 95% 98% 99% 100% 1 94% 99% 99% 100% 100% % 100% 100% 100% 100% Cleanliness Surfaces are free from contaminents -to avoid damage i.e. mirrors, crystals etc -for the science of the surface. Practical considerations. -need to minimise vibrations (no mechanical movements ion pumps) -minimise maintenance (ion pump lifetime vacuum <10-7 mbar) Author - Title (Footer) 23

24 Standardisation at ESRF Decision taken in 1990 to use CF flanges with copper gaskets Conflat flanges Stores 316LN Beamlines 304L is OK Gaskets Stores machined copper Bolts Stores silver plated For rough pumping Author - Title (Footer) 24

25 Some chambers at ESRF Author - Title (Footer) 25

26 Outline What are we dealing with? Basic beamline functions and generic solutions. Heatload Management Vacuum Supports Positioning One of the most common jobs to do for our colleagues in MEG I have got to go and draw a support! Not an interesting job but very important for the performance of the beamline. Author - Title (Footer) 26

27 Why are the supports so important? Sample Optics Machine Microbeam: ideally neither the beam or the sample should move more than 10% of its size I.e.<1-2mm We do not want to amplify the instabilities in the beam. It is important that all the optical elements and the sample are correctly supported Stability of the beam from the machine is given as 10% of its divergence Author - Title (Footer) 27

28 What do we mean by a good support? ESRF site already shows movements of the order of 1 micron. Weekends and nights are better. The support should not amplify these levels. The support should not resonate with normal driving sources. Water flow, LN2 flow, electronic fans, chillers etc. Support is not just the vacuum chamber but is also the internal mechanics.

29 The ideal support? Not an optimised support Distance floor to instrument inposed Distance instrument to support should be minimised

30 Improvement from previous version BM29 in 2008 Metallic frame Cryostat (gas?) cooled mono BM23 in 2011 Celith and marble + airlocks Author - Title (Footer) 30

31 Improvement from previous version Author - Title (Footer) 31

32 Author - Title (Footer) 32

33 Carbon Fibre Support Author - Title (Footer) 33

34 For sensitive instruments Granite base glued to the floor Height adjustment using high rigidity wedges Minimal movement or movements that can be blocked after movement Author - Title (Footer) 34

35 Outline What are we dealing with? Basic beamline functions and generic solutions. Heatload Management Vacuum Supports Positioning Author - Title (Footer) 35

36 Simplictically there are three ways of moving mechanics at ESRF Pneumatic cylinders Used on attenuators, beamviewers, valves, transfocators etc. Piezo cells Used on monochromators, mirros for fast and/or vary accurate movements Screwdrives

37 Simplictically there are three ways of moving mechanics at ESRF Pneumatic cylinders Used on attenuators, beamviewers, valves, transfocators etc. Piezo cells Used on monochromators, mirros for fast and/or vary accurate movements Screwdrives 96% of movement are actuated using some form of screw. Different accuracies are available

38 What do we mean by precision etc. Some definitions Minimum Incremental Motion The smallest motion a device is capable of delivering reliably. Not to be confused with resolution claims, which are typically based on the smallest controller display increment and which can be more than an order of magnitude more impressive than the actual motion output. There is always a compromise between speed/resolution/repeatability etc

39 What do we mean by precision etc. Some definitions Various errors or qualities can be added by the guiding elements

40 UPBL4 Dmirr Double white beam mirror with variable incidence angle. Water cooled with optimised smart profile and In/Ga cooled 2 nd mirror

41 Author - Title (Footer) 41

42 High load z movement no guiding Author - Title (Footer) 42

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44 Author - Title (Footer) 44

45 The Rolls Royce Author - Title (Footer) 45

46 UPBL4 Dmirr Double white beam mirror with variable incidence angle. Water cooled with optimised smart profile and In/Ga cooled 2 nd mirror

47 Author - Title (Footer) 47

48 The construction of an experiment is also a combination of a set of building blocks. If the building blocks are right a sophisticated experiment can be built in 2 weeks! Author - Title (Footer) 48