SUPERCONDUCTING PROTOTYPE DIPOLE COILS FOR HERA

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SUPERCONDUCTING PROTOTYPE DIPOLE COILS FOR HERA

G. Horlitz, H. Kaiser, G. Knust, K.-H. Mess, S. Wolff, P. Schmüser, B. Wiik

To cite this version:

G. Horlitz, H. Kaiser, G. Knust, K.-H. Mess, S. Wolff, et al.. SUPERCONDUCTING PROTOTYPE DIPOLE COILS FOR HERA. Journal de Physique Colloques, 1984, 45 (C1), pp.C1-255-C1-258.

�10.1051/jphyscol:1984151�. �jpa-00223707�

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Colloque C1, suppl6ment a u n o 1 , Tome 45, janvier 1984 page C1-255

SUPERCONDUCTING PROTOTYPE DIPOLE COILS FOR HERA

G. Horlitz H. Kaiser, G. Knust, K.-H. Mess, S . Wolf£, P . ~ c h m i i s e r ~ and B.H. I?iikr4

?EST, Hamburg, F. R. G.

I I . Inst. fiir ExperimentaZphysik, Univ. Hamburg, F.R.G.

'*XI. Inst. fiir ExperimentaZphysik, Univ. Hamburg and DESY, Hamburg, F. R. G.

R & s d

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Quatre prototypes d'aimants supraconducteurs de 6 m et plusieurs d'un m de long ont 6th construits. Les harmoniques restent comprises dais les tolgrances pennises pour l'op&ration d'un anneau de collision. Deux des longues bobines ont des cales longitudinales qui gliminent les contributions multipolaires d'ordre 14 et 18 prgsentes dans les aimants S 2 couches avec distribution uniforme de courant.

Abstract

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Four 6 m long and several 1 m long superconducting prototype dipoles have been built. The harmonics are within the allowed tolerances for storage ring operation. Two of the long coils have longitudinal spacers which eliminate the 14- and 18-poles present in two-shell dipole magnets with uniform current distribution.

INTRODUCTION

The proposed electron-proton collider HERA consists of a 30 GeV electron storage ring and an 820 GeV proton ring, the latter equipped with superconducting dipole and quadruple magnets. A developrent program has been started at DESY to build superconducting dipole magnets with 6.08 m magnetic length and 4.53 T nominal field. The magnets have a warm iron yoke and a cold beam pipe. This concept is rather similar to the Fermilab design. Several 1 m long prototype coils have been built and tested successfullyl. Meanwhile, four full sized coils have been produced with tooling sui- table for mass production. The last

two, labeled 6S3 and 654, have longitudinal spacers to improve the field homgeneity. As an alternative solu- tion, dipole magnets with cold iron yoke are being developed by B E , Mannheim. Two prototype quadruple magnets have been built and success- fully tested at Saclay.

M A W T DESCRIPTION

The main features of the HERA dipole magnet are shown in Fig. 1. The coil has a two-shell structure and is clamped by collars stamped from stainless steel or possibly aluminum.

Cooling is provided by onezphase

I

I I

liquid helium, surrounded by a two

phase helium return, insulating Fig. 1

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Magnet cross section. Coil ( I ) , one vacuum with superinsulation and a phase helium (2), two phase helium (3), insula- radiation shield cooled by 50 K he- ting vacuum (4), shield cooling gas (5)

,

beam lium gas. The iron yoke is at r a m vacuum tube (6), iron yoke ( 7 ) , coil support (8) temperature. The coil is supported

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984151

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Cl-256 JOURNAL DE PHYSIQUE

Table I

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Main Maq-et Parameters a t seven locations by a support structure made from fiberglass tubes. The quadru- central nominal induction Bo = 4.53 T p l e and s e x t u p l e corr-wtion c o i l s central nominal induction Bco = 4.09 T needed f o r accelerator tuning a r e wound

without yoke on t h e Seam pipe.

max. induction i n conduc- Ej,, = 4.636 T

t o r with yoke Some important magnet parameters a r e

nominal current In = 5636 A l i s t e d in Table I.+The tolerance of the number of turns n = 104 f i e l d integral i s

-

¹

-

¹

o - ~ .

The allowed inner c o i l diameter dc = 0.075 m tolerances of t h e higher h a m n i c s a r e inner yoke diameter dFe = 0.277 m summarized i n Table 111.

iron yoke width

we

⁼^0.500m

iron yoke height hFe = 0.380 m The c o i l s a r e wound from a keystoned magnetic length Jm = 6.080 m Rutherford type cable w i t h 24 strands,

each covered w i t h a 0.005 nun thick s i l v e r Table I1

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Conductor Parameters tin layer (5% Ag, 95% Sn). The main cable

parameters a r e l i s t e d in Table 11. The cable height h = 10.00 2 0.03 nun cable i s insulated by a f i r s t layer of cable inner width wl = 1.28 0.02 nun 12 nun wide and 0.025 nun thick Kapton tape cable outer width w2 = 1.67 - 0.02 nun wrapped w i t h 60% overlap and a second number of strands ns = 24 layer of 9 nun wide and 0.12 nun thick strand diameter, ds = 0.83 + 0.01 nun g l a s s f i b e r tape which is impregnated

untinned with 21 % (per weight) of B stage e p x y

copper/supercon- a = 1.8 L O . l w i t h a ~ i n g t e m p e r a t u r e o f 1 6 0 0 C . I n ductor r a t i o t h e second layer there a r e gaps of 3 nun diameter of f i l a - df = 0.01 02 0. O O h t o allow f o r helium penetration i n t o t h e

ments cable.

number of filaments nf 2. 2460

filament p i t c h pf = 25 nun Fig. 2 shows a cross section of c o i l s 6S3 cable t w i s t pitch pc < ⁹⁵nun and 6S4. The inner s h e l l has 32 turns per nominal operating In = 5635 A half c o i l , the outer 20 turns. After t h e

current fourth turn of e i t h e r s h e l l longitudinal

specified c r i t i c a l I,,,, = 6318 A GI1 wedges a r e inserted t o remove t h e 14- short sample and 18-pole f i e l d s which a r e present i n current in

cable a t T=4.6 K and B = 5.5 T

two-shell c o i l s with uniform current dis- 4

tribution. A t the c o i l heads of t h e inner 2

s h e l l , GI1 spacers a r e placed behind turns 6

1, 4, 7, 10 and 27 (see Fig. 3) i n order 7

t o avoid a f i e l d enhancement a t t h e conductor and t o minimize t h e s e x t u p l e and d e c a p l e f i e l d s generated by the c o i l ends. The upper and lower half c o i l s a r e wound separately. After winding and curing t h e inner s h e l l i s covered w i t h a 0.5 nun thick GI1 layer with s l o t s f o r helium penetration. Then a 10 cm long s p l i c e i s made and t h e outer s h e l l i s wound on top.

The winding mandrel, the keys f o r t h e c o d angles and t h e curing molds a r e assembled from punched laminations i n order t o assure high cross sectional

accuracy. Fig. 2 - Coil cross section. Inner c o i l

layer ( 1 )

,

outer c o i l layer (2)

,

longi- The finished upper and lower half c o i l s tudinal wedges ( 3 ) , G I 1 layer ( 4 ) , c o i l are assembled around a cylindrical mandrel insulation ( 5 ) , s t a i n l e s s s t e e l c o l l a r s equipped with two quench heaters a t the ( 6 ) , longitudinal rods ( 7 ) , R1 = 37.50 nun surface of t h e outer c o i l s h e l l and in- R2 = 47.76 nun, R3 = 48.25 nun, R4 = s u l a t e d w i t h 6 l a y e r s o f 0.125mKapton 58.51 nun,cpl = 76.74O,q2= 41.11°, f o i l . Shims a r e inserted t o f i x t h e a ? = 4.84O, a2 = 4.85O

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Ilona stacks of stainless steel clamps, made from stamp& l-- nations, are placed around the coil from the top and the bottom. The collared coil is corn pressed to its final shape with a force of about 4.5 106 N/m.

The collars are locked by pul- ling 10 mm thick steel rods through the holes in the mid- plane (see Fig. 2). The rods can be removed if a field mea- surement should indicate that a reshirtuning of the coil is necessary. The top and bottom half coils are connected by a 10 cm long solder joint.

TESTS AND ~ S U L T S

Each clamped coil was investi- Fig. 3

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Coil head (inner layer), GI1 spacers gated for ground and turn- to-

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,

GI 1 longitudinal wedges (6, 7) turn shorts. A warm short between two turns was found in coil 6S2. The field harmonics were measured at room temperature along the whole coil length. Most of the harmonic coefficients are well within the required limits. The coils with longitudinal spacers have 14- and 18-poles belm 2

.

¹

^o-~.

So far, cryogenic measurements have been performed only with two 1 m long coils with the same geometry as that of coils 6S1 and 6S2. The short sample critical current of the cable was reached after 4 and 13 training steps, respectively. The quench current was found to depend linearly on the temperature in the range 3.8 K to 5.0 K.

The hanmnics at helium temperature are listed inTable 111. They are generally within the required tolerances. The current dependence of the lower h m n i c s is plotted in Fig. 4. The sextuple shows the well known hysteresis due to persistent currents but is constant at high currents. This indicates that the coils are clamped

with sufficient precom- Table 111

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Straight section harmonics without iron pression.

yoke (at r = 2.5 cm, relative to Bo) at 6000 A for 1 m

long prototypes IS1 and IS2 A vertical bath cryostat for testing the 6 m long coils has just been finished and is now being used to test coil 6S2.

Meanwhile the assembly of coil 6S1 within its origi- nal cryostat and iron yoke is nearly ready and a test of a complete magnet can start soon.

harmonic no.

n 1 2 3 4 5 6 7 8 9

*

design value -1 .I for 1 Sl

,

^{7.8 for}^{1 S2}

coil 1 S 1

&XI

o4

anxl

o4

-0.5 4.3 -1.1 0.2 0.3 0.0 -0.7 0.0 -0.4 0.7 14.1 -0.6 o.o** 0.0**

-12.6 0.5 design values

bnx104 10000.

0. '2.5 -1.1,7.8*~6.0

0. -2.0 0. '2.0 0.

14.9 0.

-13.2

**

used for off center correction of the measuring coil system

coil 1 S 2

%XI

o4

anxl

o4

-2.3 0.7 7.9 -0.2 -0.7 -0.6 -1.2 0.3 0.2 0.4 14.5 -0.4

o.o** 0.0**

-11.8 0.3 We would like to express our gratitude to all tech- nicians, enqineers and scientists who have con- tributed to the design, fabrication and tests of these magnets.

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C1-258 JOURNAL DE PHYSIQUE

Fig. 4

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Straight section harmonics without iron yoke, 1 m prototype coils IS1 ( 0 ) and 152 (x)

.

Deviation of n o d harmonics Ab2 (quadruple) and Abj (sextuple) and skew harmonics Aa2 and Aa3 from design values

(b2 = a2 = a3 = 0, bj =

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^1.1 ^x10-4 for coil IS1 and b3 = 7.8 x 10-4 for coil 1S2) versus current.

1. G. Horlitz, H. Kaiser, G. Knust, K.-H.&ss, P. Schmiiser, B. H. Wiik, S. Wolff "Perfor- mance of 1 m long/75 m Bore Superconducting Prototype Coils for HERA", Proc. Part. Acc.

Ccmf. Santa Fe, 1983. I- mans. Nuc. Sci.

NS-30, 3390 (1983), preprint DESY 83-020, March 1983