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CERN CH-1211 Geneva 23 Switzerland EDMS NO. REV. VALIDITY XXXXXXX 0.1 DRAFT REFERENCE TE-MSC-MM-XXXX Date: 2017-07-31 ENGINEERING NOTE MEASUREMENT REPORT OF ESS DRIFT TUBE LINAC ABSTRACT: This document reports the main results of the magnetic measurements of the first permanent prototype of the assembled ESS drift tube linac from INFN containing the PMQ00. PREPARED BY: TO BE CHECKED BY: TO BE APPROVED BY: G. Golluccio S. Russenschuck M. Buzio S. Russenschuck F. Grespan (INFN) REFERENCE EDMS NO. REV. VALIDITY TE-MSC-MM-XXXX XXXXXXX 0.1 DRAFT Page 2 of 9 DISTRIBUTION LIST: S. Russenschuck M. Buzio F. Grespan REFERENCE EDMS NO. REV. VALIDITY TE-MSC-MM-XXXX XXXXXXX 0.1 DRAFT Page 3 of 9 HISTORY OF CHANGES REV. NO. DATE PAGES 0.1 2017-04-26 All DESCRIPTIONS OF THE CHANGES First version REFERENCE EDMS NO. REV. VALIDITY TE-MSC-MM-XXXX XXXXXXX 0.1 DRAFT Page 4 of 9 TABLE OF CONTENTS 1. Introduction ........................................................................................................ 5 2. Integrated STRENGTH ........................................................................................... 6 3. field quality ......................................................................................................... 6 4. Magnetic Centre ................................................................................................... 7 5. Conclusions ......................................................................................................... 8 6. REFERENCES ....................................................................................................... 9 REFERENCE EDMS NO. REV. VALIDITY TE-MSC-MM-XXXX XXXXXXX 0.1 DRAFT Page 5 of 9 1. INTRODUCTION This document reports the main results of the magnetic measurements of the first prototype of a drift tube linac (DTL) assembled, holding the Permanent Magnet Quadrupole (PMQ) produced from the INFN. The measurement has been performed with systems and procedures [1], [2] already used to measure similar magnets of the CERN Linac4 drift tube. Two independent measurement methods have been applied to verify the integrated gradient and the magnetic centre of the quadrupole, the Single Stretched Wire [3], compared to the fiducials on the DTL stem. A rotating coil [2] to compare the field homogeneity before and after the assembly of the magnet in the DTL. In the following table is reported the test summary. Magnet Rotating coil test Stretched wire (SSW) test Manufacturer ID Notes Bench Date Coil shaft Measurement radius [mm] Temperature [ºC] Bench Date System Temperature [ºC] INFN PMQ00 Bldg. I8 09 Jan. 2017 SRC-1 ‘Linac’ (400 mm) 7.5 25 Wire bench ‘4’ 17 Jan. 2017 SSW4 25 Table 1- Test Summary The magnet parameters are reported in Table 2 as indicated in the magnetic measurement request. Manufacturer INFN ID PROTO DTL (PMQ00) Yoke length [mm] 45 Weight [kg] 5 Aperture radius [mm] 20 Excitation 16 Permanent magnets Sm2Co17. Nominal gradient [T/m] 65 Nominal integrated 2.925 gradient [Tm/m] Magnetic length [mm] 45 Tolerance integrated 50·10-4 Gradient Table 2- magnet parameters Summary The sensitivity coefficients of the shaft SRC-1 ‘Linac’ have been calibrated the 22/02/2013 with a previous ‘in-situ’ calibration [4] performed with a CERN reference magnet in the same area used for the PMQ00 measurements. The reference frame has been defined as for the Linac4 quadrupoles, as shown below: REFERENCE EDMS NO. REV. VALIDITY TE-MSC-MM-XXXX XXXXXXX 0.1 DRAFT Page 6 of 9 ID tag Y Field direction (roll) + Pin 1 beam direction Pin 2 X Z Figure 1: Reference frame of the magnetic measurements In this reference frame the quadrupole field seen from the beam upstream is normal positive. The same reference frame is used for the stretched wire and the rotating coil system. 2. INTEGRATED STRENGTH The integrated quadrupole field of the DTL has been measured with both a stretched wire and a rotating coil and it has been compared to the nominal (expected) values. Results are given in Table 3. Measured Naked PMQ00 Measured PMQ in the DTL SSW 2.869 2.871 ROTATING COIL 2.866 2.865 Estimated Uncertainty Unit 0.003 Tm/m 1·10 0.005 1.7·10-3 Tm/m - -3 Table 3 - integrated gradient measurement The integrated gradient is positive in both measurement systems and corresponds to the defined polarity from the design. The measurements are in agreement within their 1-σ uncertainties. According to those results the assembly process has not shown relevant changes in the magnet gradient. 3. FIELD QUALITY The average field harmonics have been measured with a rotating coil using the flipping method [2] for the naked PMQ. It is based on the mechanical rotation of the magnet with respect to the coil rotation axis, this method is detailed in [2]. The mechanical rotation is 6 different positions allows to remove systematic errors due to coil rotation imperfections. Those measurements has been compared with the one performed on the assembled DTL to check if the assembly process has an impact on the field quality. Has to be noted that, due to the presence of the DTL, only one position has been used to measure the harmonics of the DTL REFERENCE EDMS NO. REV. VALIDITY TE-MSC-MM-XXXX XXXXXXX 0.1 DRAFT Page 7 of 9 and the systematic errors has been suppressed using a digital bucking of the three coils in the SRC-1 shaft. The measurement results for the harmonics measured before and after the assembly at the reference radius of 7.5 mm are reported in fig.2 with the relative 1-σ uncertainty error bars. Figure 2: Average field harmonics with 1 error bars. In the table below we report the measured harmonics up to the 10th. DTL PMQ00 Estimated assembled Uncertainty Tolerance n Unit bn an bn an bn an 3 units @ 7.5 mm -8.2 -14.2 -7.7 -10.8 2.6 2.4 100 4 units @ 7.5 mm 10.7 -2.1 12.7 -7.0 1.2 1.4 100 5 6 7 8 9 10 -7.4 36.3 -1.7 0.4 1.0 -0.3 0.6 3.4 4.8 -0.4 0.5 -0.4 -9.8 32.4 0.2 -1.0 -1.1 -7.7 2.4 1.0 3.0 0.6 0.2 -10.8 3.0 0.6 0.7 0.3 1.7 1.9 2.8 0.6 0.7 1.4 1.5 1.9 Pass OK OK 100 units @ 7.5 mm OK 100 units @ 7.5 mm OK 100 units @ 7.5 mm OK 100 units @ 7.5 mm OK 100 units @ 7.5 mm OK 100 units @ 7.5 mm OK Table 4 - average harmonic errors The magnet homogeneity is within the tolerance at the 7.5 mm measurement radius for the harmonic order up to 10. The highest harmonic is the number 6 as allowed by the quadrupole geometry. 4. MAGNETIC CENTRE The magnetic axis of the quadrupole has been measured with the stretched wire system The axis measurement are reported taking as a reference the pin holes named in figure 3 as point 1 and 2. The reference frame of the measurement is defined in figure 4. The x positive axis is REFERENCE EDMS NO. REV. VALIDITY TE-MSC-MM-XXXX XXXXXXX 0.1 DRAFT Page 8 of 9 defined by the line passing by the points 2 to 1, while the z from stage A to B (see fig. 4), aligned to the magnet axis. The origin of the reference system is in point 1. In this coordinate system the magnetic axis is located at x = -426.19 mm and y= -25.40 mm. Figure 3: pin holes for fiducialization. Figure 3: reference frame of the SSW. 5. CONCLUSIONS The prototype PMQ00 after installation in the DTL has not changed in terms of field harmonics and field strength, within the accuracy of the measurement systems. The magnet axis has been fiducialiazed with respect to a mechanical frame defined on the DTL, the offsets measured must be verified by mechanical measurement on the DTL. REFERENCE EDMS NO. REV. VALIDITY TE-MSC-MM-XXXX XXXXXXX 0.1 DRAFT Page 9 of 9 6. REFERENCES [1] [2] [3] [4] M. Buzio et al. , “Magnetic qualification of Permanent Magnet Quadrupoles for CERN's Linac4”, EDMS [1138960] G. Golluccio et al., “A polyvalent harmonic coil testing method for small-aperture magnets”, Rev Sci Instrum. 2012 Aug;83(8):085116. doi: 10.1063/1.4746281. J. Di Marco et al., “Field alignment of quadrupole magnets for the LHC interaction regions”, IEEE Trans. Appl. Supercond., vol. 10, 2000. G. Golluccio et al., “In situ calibration of rotating sensor coils for magnet testing”. Rev Sci Instrum. 2012 Jan;83(1):013306. doi: 10.1063/1.3675578.