Short functional description

Gyrotron SCM system

Short functional descriptions of the ITER European-supplied Gyrotron Superconducting Magnet system

Any company in Europe able to provide such system is invited to register on F4E Industryportal and notify it to F4E through the email

Short functional description

Gyrotron SCM system

1. INTRODUCTION

This document presents, for information only, a short functional description of the Superconducting Magnet (SCM) system for the European 2MW gyrotron at 170GHz for the ITER Electron Cyclotron (EC) system. Mainly the requirements on magnetic field profiles and accuracy, overall geometry interfaces, and stability requirements are shown.

The SCM system consists of the complete superconducting magnet with its cryostat containing several superconducting windings, control/protection/monitoring systems, and any other components deemed necessary by the supplier to operate the SCM reliably at the specified performance.

Fusion for Energy plans to launch in 2011 a Call for Tender for a new SCM system for the EU gyrotron compatible with the ITER Organization requirement of not having cryogenic lines connected to the system nor frequent (< 1year) re-fillings with cryogenic fluids.

This document is not the technical specification of the planned Call for Tender.

The procurement activity, subject to the approval of the F4E Work Programme, would include:

-The design and analysis of the complete supply

-Production of manufacturing drawings

-Procurement of any required materials and component

-Use of any equipment and/or facility required for manufacturing and testing in factory

-Fabrication and assembly

-Factory testing

-Packing and shipping

-Installation and on-site testing

-Quality assurance and control

-Documentation, including design report, materials and components qualification and verification, factory test reports installation procedures/instructionsoperation and maintenance manuals, as applicable and quality assurance (QA);

2. FUNCTIONAL DESCRIPTION OF THE SCM SYSTEM

2.1Coil Specifications

The required field produced by the SCM is given below.

The reference coordinate system used is an orthogonal reference system (x-y-z) with the z-axis corresponding to the geometrical axis of the SCM warm bore. The origin of the z-axis is defined consistently with the z-axis given in Table 1. When cylindrical coordinates are used the radial position r is defined as: r = Sqrt(x2+y2).

i) Nominal on axis B-field value at zC = 499.5mm : B0=6.86T

The magnet should be designed such to allow operation at a maximum magnetic field 5% higher than the nominal field.

ii) Axial profile Bz(z) along the magnetic axis (r = 0): see Table 1

iii)Along the magnetic axis given in Table 1, four specific positions will have the following labels:

- position A (zA = -82.mm) SCM bottom flange

- position B (zB = 118.5mm) is the middle point of the cathode

- position C (zC = 499.5mm) is the middle point of the gyrotron cavity

- position D (zD = 810mm) SCM top flange (gyrotron rest plane)

The SCM top flange is the rest plane of the gyrotron (position D) and is defined as the mechanical reference of the entire magnet and gyrotron assembly. It is therefore extremely important that the mechanical design of the top flange is compatible with this definition. The design of this flange should take into account all possible deformations due to the magnet vacuum and/or the gyrotron. In the attached drawing, a SCM interface drawing defining the above mentioned mechanical criteria and other interfaces criteria is given.

iv)The maximum deviation of the magnetic field axis with respect to the mechanical axis defined by the reference plane at the top plate of the cryostat will be less than 0.15mm between positions A and D defined in point iii). The alignment must be performed by changing the position of the superconducting coils with respect to the mechanical axis at helium temperature. This alignment once performed during the on site acceptance test shall not need any further realignment in case of quench and/or magnet warm-up to room temperature during the guaranteed period of the magnet.

v)The on axis magnetic field deviation between the values given in Table 3 and the measured values, assuming an axial position accuracy of the Hall probe of z≤0.2mm, has to be within the following ranges:

- between positions A and D (outside cavity region): Bz/Bz≤0.5%

- cavity region, zc±20mm: Bz/Bz≤0.1%

vi)All the solenoidal coils must be wound on a common mandrel to insure that the magnetic axis is a well defined straight line.

vii)The magnet design has to be such that an independent adjustment of the magnetic field amplitude (Bz) at positions B and C and the gradient (dBz/dz) at position B is possible within the ranges defined in pt. x)

viii) It is important that the magnetic field generated by the coils is symmetric about the middle z-position between the coils and that this position is centered at zB = +118.5mm ±0.5mm (position B).

ix)Around the nominal value given in Table 1, further cases will be possible to achieve for positions B and C, each one being independent from the other ones:

range of BBBBnom±10%

range of (dB/dz)B(dB/dz)Bnom±10%

where (dB/dz)Bnom= 5.4 10-4 [T/m] (on-axis Bz gradient @ zB)

range of BCBCnom ±5%

For alignment purposes it is needed to energize the solenoidal coils Separately with individually different currents. For this, additional current leads have to be provided. The additional current leads will be used only during the alignment procedure which will typically last during a few days per year. During normal gyrotron operation at the nominal field current will be flowing in the additional current leads. The maximum current in the additional current leads is 45.9A.

x)No ferromagnetic material is allowed in the SCM.

xi)For continuous current controlling in the different coils, the SCM will never be used in persistent-mode.

z
[mm] / Bz
[T] / z
[mm] / Bz
[T] / z
[mm] / Bz
[T] / z
[mm] / Bz
[T] / z
[mm] / Bz
[T]
0 / 0.21595 / 175 / 0.37235 / 469 / 6.80265 / 779 / 2.53222 / 1129 / 0.25796
5 / 0.21735 / 180 / 0.40552 / 479 / 6.83657 / 789 / 2.34437 / 1139 / 0.24580
10 / 0.21861 / 185 / 0.44359 / 484 / 6.84809 / 799 / 2.16895 / 1149 / 0.23439
15 / 0.21973 / 190 / 0.48694 / 489 / 6.85624 / 809 / 2.00592 / 1159 / 0.22367
20 / 0.22069 / 195 / 0.53596 / 494 / 6.86116 / 819 / 1.85499 / 1169 / 0.21359
25 / 0.22150 / 200 / 0.59098 / 499 / 6.86301 / 829 / 1.71572 / 1179 / 0.20410
30 / 0.22215 / 205 / 0.65232 / 504 / 6.86190 / 839 / 1.58752 / 1189 / 0.19517
35 / 0.22264 / 210 / 0.72027 / 509 / 6.85793 / 849 / 1.46974 / 1199 / 0.18674
40 / 0.22295 / 215 / 0.79508 / 514 / 6.85116 / 859 / 1.36169 / 1209 / 0.17880
45 / 0.22310 / 220 / 0.87695 / 519 / 6.84163 / 869 / 1.26264 / 1219 / 0.17129
50 / 0.22309 / 225 / 0.96602 / 529 / 6.81439 / 879 / 1.17189 / 1229 / 0.16420
55 / 0.22293 / 230 / 1.06238 / 539 / 6.77614 / 889 / 1.08877 / 1239 / 0.15750
60 / 0.22263 / 235 / 1.16606 / 549 / 6.72656 / 899 / 1.01264 / 1249 / 0.15115
65 / 0.22220 / 249 / 1.49477 / 559 / 6.66512 / 909 / 0.94287 / 1259 / 0.14514
70 / 0.22168 / 259 / 1.76257 / 569 / 6.59120 / 919 / 0.87892 / 1269 / 0.13944
75 / 0.22109 / 269 / 2.05510 / 579 / 6.50415 / 929 / 0.82025 / 1279 / 0.13404
80 / 0.22048 / 279 / 2.36883 / 589 / 6.40332 / 939 / 0.76639 / 1289 / 0.12891
85 / 0.21989 / 289 / 2.69937 / 599 / 6.28816 / 949 / 0.71690 / 1299 / 0.12404
90 / 0.21940 / 299 / 3.04169 / 609 / 6.15820 / 959 / 0.67138 / 1309 / 0.11941
95 / 0.21908 / 309 / 3.39035 / 619 / 6.01315 / 969 / 0.62948 / 1319 / 0.11501
100 / 0.21902 / 319 / 3.73977 / 629 / 5.85294 / 979 / 0.59086 / 1329 / 0.11082
105 / 0.21933 / 329 / 4.08449 / 639 / 5.67775 / 989 / 0.55523 / 1339 / 0.10683
110 / 0.22013 / 339 / 4.41940 / 649 / 5.48807 / 999 / 0.52232 / 1349 / 0.10304
115 / 0.22156 / 349 / 4.73997 / 659 / 5.28478 / 1009 / 0.49189 / 1359 / 0.09942
120 / 0.22380 / 359 / 5.04236 / 669 / 5.06914 / 1019 / 0.46372 / 1369 / 0.09596
125 / 0.22704 / 369 / 5.32352 / 679 / 4.84284 / 1029 / 0.43761 / 1379 / 0.09267
130 / 0.23148 / 379 / 5.58118 / 689 / 4.60799 / 1039 / 0.41338 / 1389 / 0.08952
135 / 0.23736 / 389 / 5.81388 / 699 / 4.36703 / 1049 / 0.39088 / 1399 / 0.08652
140 / 0.24494 / 399 / 6.02089 / 709 / 4.12264 / 1059 / 0.36995 / 1409 / 0.08365
145 / 0.25451 / 409 / 6.20210 / 719 / 3.87764 / 1069 / 0.35047 / 1419 / 0.08090
150 / 0.26638 / 419 / 6.35801 / 729 / 3.63480 / 1079 / 0.33232 / 1429 / 0.07827
155 / 0.28087 / 429 / 6.48956 / 739 / 3.39674 / 1089 / 0.31538 / 1439 / 0.07576
160 / 0.29834 / 439 / 6.59810 / 749 / 3.16574 / 1099 / 0.29956 / 1449 / 0.07335
165 / 0.31915 / 449 / 6.68525 / 759 / 2.94374 / 1109 / 0.28477 / 1459 / 0.07104
170 / 0.34369 / 459 / 6.75281 / 769 / 2.73222 / 1119 / 0.27093 / 1469 / 0.06883

Table 1: Nominal Magnetic field distribution along the magnetic axis of the SCM.

xii)The magnet has to withstand any quench event at fully charged coils. The magnetic axis must not be shifted, the alignment defined in pt. v) above has to be maintained after any quench.

xiii)The horizontal shift of the magnetic axis with respect to the geometrical axis must have a long term stability (one year) of 0.1 mm assuming 3 warm-up/cool-down cycles per year.

xiv)All the electrically live parts (including control and instrumentation electronics) of the SCM must be electrically insulated against the cryostat for a minimum voltage of 1000 V with respect to ground.

xv)The SCM will be mechanically sustained by an Aluminum plate via a sustaining ring welded on the SCM. In case of quench, currents might be induced in the plate. The SCM must stand safely these conditions.

xvi)In addition to the solenoidal coils described above, a set of transverse field dipole coils must be fitted. These dipole coils will be used only for verifying some gyrotron alignment properties while the gyrotron is mounted inside the SCM. For normal operation of the gyrotron these dipole coils will not be energized.

xvii)The geometry of these dipole coils has to be such that a transverse field on axis in two orthogonal directions (x and y), with the z-axis corresponding to the main magnetic axis, can be generated.

xviii)Since these dipole coils will be used for checking the gyrotron electron beam alignment, for a given current in the dipole coils, a high degree of symmetry in the transverse fields on the magnetic axis has to be achieved as specified below (Clause xxii).

xix)At the current settings for the nominal axial field, for a field line starting at position: zB = 118.5mm, r = 57.2mm, the dipole coil should allow a nearly parallel displacement of the field line at the cavity center by a minimum of 1mm (x and y axis). For example, the field line versus axial distance is shown in Figure 1 for a field line starting on the mechanical axis at position zB = 118.5mm, r = 0mm. In this same figure, the transverse field, Bx(z), on the mechanical axis is also shown. In Figure 2, the transverse field Bx(z) on the mechanical axis, are shown for each set of dipole coils energized separately.

For any given set of dipole coils (x or y), and with the magnetic field axis aligned on the mechanical axis, the dipole coil design must be made such that for any given on-axis z-position, the relative variation of the absolute transverse field amplitude is less than 2% when the dipole coil current is reversed.

xx)Any difficulties in fulfilling Clause xxii) above should be clearly mentioned. It should be possible to energise each set of dipole coils separately.

xxi)The expected operational life of the magnet shall be of at least fifteen years.

Figure 1

Figure 2

2.2Mechanical Specifications

The gyrotron tube must be inserted into the warm bore of the SCM cryostat which must support the entire weight of the gyrotron. The mechanical axis of the gyrotron is adjusted to coincide with the magnetic axis of the SCM. The mechanical reference plane must be accurately machined as well as a reference surface on the warm bore, which will be used as a reference for defining the mechanical axis. The precise design of these surfaces will be defined and mutually agreed. The design of the warm bore and top and bottom cryostat flanges must be agreed upon.

Free space for the gyrotron must be maintained both above the top, and below the bottom of the cryostat. Although the gyrotron itself is constructed of non-ferromagnetic materials, there are additional copper magnet coils associated with its operation. One of these coils is operated in AC at a maximum frequency of 50Hz. The maximum field generated by these coils at the SCM top plate (mechanical reference) is lower than 1 mT (10Gauss).

The following specifications will ensure that the gyrotron can be placed aligned and supported in the SCM and will be able to function properly:

i)Weight of the gyrotron; to be supported by the top of the cryostat:2000 kg

This weight is distributed on a ring with a inner and outer diameters of about 450/650 [mm]. At a radial position outside the ring (~650-750mm) threads will be machined on the SCM top plate for fixing a high voltage insulating ring to be placed between the gyrotron and the SCM top plate. The details will be agreed during the design phase.

ii)The design of the top flange should be mainly based on the mechanical stability of this flange with respect to the mechanical stresses induced by the vacuum inside the cryostat and the gyrotron weight.

iii)Weight to be supported by the sustaining ring welded on the cryostat

outer diameter (including gyrotron) 2300 kg

The axial position of this ring must be agreed upon during the design phase before manufacture may commence.

iv)In order to fix an HV-insulating oil tank for the gyrotron-socket under the cryostat, threads will be machined in the bottom SCM plate.

The surface quality (machined surfaces for O-rings) has to be improved in the areas between the diameters of 400mm and 650mm. The roughness of the machined surfaces should be lower than Ra< 1.6µm.

v)Diameter of required free space on the top SCM flange: 850 mm

vi)The position of the cold heads and the necks for the safety valves and the current feed-throughs must be compatible with the gyrotron design and must be agreed upon.

vii)Distance between the cryostat top (top flange) and position B (zB = 118.5mm) 691.5 mm

viii)Distance between the cryostat bottom flange and position B: 200 mm

ix)Minimum diameter of the warm bore: 220 mm ±0.1mm

x)On axis magnetic field measured after a quench must meet the coils stability specifications of section 2.1.

xi)On axis magnetic field measured after two (2) cold-warm-cold cycles must meet the coils stability specifications of section 2.1.

2.3Cryogenic and Safety Specifications

The SCM system must be able to operate at the nominal operating conditions with neither cryogenic lines connected nor need of regular re-fillings with cryogenic fluids. Frequency of re-fillings shall be less than 1 year.

The SCM must provide easy operation as well as adequate safety for personnel and associated equipment, especially in case of a quench.

Quench detection and protection circuit capable of dissipating the stored energy of the magnet at its maximum operating field without damage to the coils.

The electronic components and devices described in this section will be called in the rest of the call for tender "the ancillary electronics".

2.4Line Voltage

The available power sources are 50Hz – 230V(±10%), single phase and 50Hz – 400V(±10%), three phases. All ancillary electronics must be compatible with these sources and must be supplied with 30m of shielded cable to connect the electronics to the SCM.

The inputs and outputs of all ancillary electronics must be floating with respect to ground. The associated electronics must be floating with respect to ground and to the SCM. The insulation voltage must be at least 1000V.