Magnetic Field Measurement System For Cryogenic Permanent Magnet Undulator At SSRF

Transcription

1 Magnetic Field Measurement System For Cryogenic Permanent Magnet Undulator At SSRF Hongfei Wang, Jingmin Zhang,Wei Zhang, Qiaogen Zhou Shanghai Institute of Applied Physics, P.O.Box , Shanghai , P. R. China

2 Outline 一. Local field measurement System 二. Measurement setup and activities 三. Measurement results Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 2

3 The overall view The motivation of building the Measurement system is to finish magnetic measurement at in- Vacuum and cryogenic condition. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 3

4 Parameters Of CPMU20 Structure Period Length Period number Magnet and size (mm) Hybrid 80 N48H/NdFeB(65W 25H 6.2D) Pole and size (mm) Gap Range Efficient Peak DT4C/(43W 20H 3.4D) 5-30mm Efficient Peak Phase Error <5 Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 4

5 Layout of magnetic measurement system Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 5

6 Mechanical System platform A set of MMF is assembled into vacuum chamber. We adjust the rods between inside beam and outside beam according to magnetic field results measured at cryogenic condition. The seven platforms can be used to coarse the straightness of the guide rail. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 6

7 Top view Of the MMF An aluminum beam is set into the vacuum chamber. It is supported by seven rods which connected outside supporter. A guide rail is assembled on the beam. The hall probe and three retro reflectors are assembled on the sliding block of the rail. A stretched wire system used to measure the magnetic integral and the real gap of the CPMU at cryogenic condition is also set into the chamber. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 7

8 Mechanical Drive Two wheels are used to drive the hall prove moving by a steel rope. The wheels are connected with two step motors by two magnetic fluid devices in order to get vacuum. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 8

9 In vacuum linear plate It can be used to adjust the height of hall probe in order to find the center at vertical direction at vacuum condition. The screw pitch of the plate is 0.5mm,and its precision is 5um. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 9

10 Laser measurement systems Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 10

11 Quartz glass window Parameter of the glass window 1)diameter:200mm 2)thickness:20mm 3)coating film:ar(light transmittance 97%) 4)Flatness:63nm 5)Insulation :10-10mbar Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 11

12 Measurement setup and activities

13 Measurement activity The refrigeration copper pipe Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 13

14 Measurement activity angle reflector Straightness reflector Hs20 laser ruler XL80 for measuring the rail s yaw Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 14

15 Field test situations Straightness interferometer Guide rail Platform for adjusting height Igus chain Angle retro reflector Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 15

16 3-D Hall probe The ADC hall probe is designed with 3 orthogonal axes, see figure below. This probe uses three FW Bell GH-700 hall sensors (see specifications in figure 3) with the addition of an on board RTD for temperature measurement. ADC has designed this probe using 4 layer board technology. All signals lines are embedded between two layers of copper to reduce noise. M a g n e t i c F i e l d ( G s ) y = x 6 Volt(V) x x x x x Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 16

17 Find the center at Y direction The magnetic measurements are done with hall probe at three different height in order to find the center of every point at y direction M=F y=ay +by+c ( ) M magnetic field : y position at vertical direcition : a, b, c: the coefficients from polynomial fitting S t r a ig h t n e s s o f t h e g u i d e r a i l a t y d i r e c t io n ( m m ) Longitudinal position(mm) 141K 298K 400mm-2000mm The measurement range is from 0 to 2400mm. The step is 0.5mm. The vertical straightness results in more than 1.5 rms phase error before calibration. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 17

18 The yaw of the guide rail at room and Cryogen temperature Y a w o f t h e g u i d e r a i l ( d e g r e e ) K 298k points number The yaw of the guide rail at room temperature happen big changes compare to the cryogenic temperature. The yaw of the rail results in more than 1 rms phase error before calibration. A periodic wave occurs in the angle curve. The position of the period fluctuation are just near by mounting holes of the guide rail. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 18

19 Measurement 8 Phase Error(Deg ) No1 No2 No3 No Pole Num Repeatability<0.1 Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 19

20 Gap measurement in vacuum condition This method is from ESRF. The stretched wire is used to measure the gap. When the wire with 0.124mm diameter touches the contact probe, the resistor value is close to zero. The precision is about 5um. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 20

21 Measurement results

22 Magnetic field data at different Temp( ) RMS Phase Error (Deg) Peak Field(T) Effective Field (T) Period Length (mm) Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 22

23 Magnetic field data at different 130K-150K dbe/dk<2gs/k 150K-250K dbe/dk<3gs/k The maximum peak field occurs at 141k. The RMS phase error is 4.35 with 6mm gap and 141k temperature. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 23

24 Magnetic field data at different Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 24

25 Compare between room temp and Cryogenic temp The drop of temp results in changes of the phase error and trajectory Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 25

26 Changes of magnetic field when temp drops from room temp to cryogenic temp db/b Pole Number System error From the deformation Of the inside beams in Cryogenic temperature Random error From the longitudinal irregular change of the magnet assembly arrays. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 26

27 Changes of magnetic field when temp drops from room temp to cryogenic temp The gap of the CPMU relatively varies from room temperature to low temperature because of the mechanical contraction of the stems and the magnetic force increasing Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 27

28 Two test results in 2014 and 2015 R M S P h a s e E rro r D e g Temperature K This year,the rods are readjusted in order to make the RMS phase error better than 3 at 6mm gap in 141K temperature. The data indicate a fact that the optimal results can be achieved by adjusting the rods. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 28

29 Conclusions 1. The measurement repeatability is better than 0.1 degree. 2. The yaw and straightness of the guide rail can be measured by two XL80 laser systems. The longitudinal position is also measured by HS20 laser ruler; 3. The height of hall probe is adjustable. 4. The x direction position can t be adjusted. We should work hard to achieve it in future. 5. Stretched wire system finishes the measure of the gap, but can t do the integral field measurement well, because the repeatability is not good. Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 29

30 Shanghai Institute of Applied Physics, C.A.S Oct IMMW19 30