Download pmq00_drift_tube_measurement_report

CERN CH-1211 Geneva 23 Switzerland
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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)
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DISTRIBUTION LIST:
S. Russenschuck
M. Buzio
F. Grespan
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HISTORY OF CHANGES
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All
DESCRIPTIONS OF THE CHANGES
First version
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TABLE OF CONTENTS
1.
Introduction ........................................................................................................ 5
2.
Integrated STRENGTH ........................................................................................... 6
3.
field quality ......................................................................................................... 6
4.
Magnetic Centre ................................................................................................... 7
5.
Conclusions ......................................................................................................... 8
6.
REFERENCES ....................................................................................................... 9
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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:
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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
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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
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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.
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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.