NBI 2002
14-19 MARCH, 2002

Magnetic Horns and Target of K2K
Y. Yamanoi (KEK)
Contents•
Introduction––•

Modification and results––•

Bending & vibration
New disk and dumping time

Spray cooling system––––••

Target and Horns layout in beam line cave
K2K Horn design

pH control
Alumite growth
Tritium accumulation
Effect eliminator

Durability test
SummaryNBI 2002
14-19 MARCH, 2002

Target and Horns layout
Target & First HORN
Second HORN

1.05°Beam•••

Pulse Current•••

Built-in production target (φ30mm)(Blue) Removable train:-A distance between horns is about 8.06 m.
(Green) Adjustment table:-decline to Super-Kamiokande with 1.05°-Accuracy is equal to about 0.04 mrad.
Operation current 250k Amp at both horns
High pulsed current 2.5ms width, 2.18s cycle
Total Joule’s heat=7740 kcal/hNBI 2002
14-19 MARCH, 2002

Soil

Target and Horns in caveConcreteRail,
5-ton craneTarget3.7m 2.15

Decay PipeＩｒｏｎBeam

2.15

SK17m

Stripline-2

Transformer1,2

Cave size (W3.7m, H3.8m, L17m)
Cave – Radioactive air is closed simplify.
Both transformers is set inside beam line.
Stripline-1 : 9.3m, (Cross section t15mmx320mm)
Stripline-2 :12.0m, (Cross section t15mmx320mm)

Stripline-1

Top view

NBI 2002
14-19 MARCH, 2002

First Horn
12 GeV proton～6e12 ppp

Φ0.62 m2.364 mBeam height
1.96m•12GeV PS cycle=2.18 s•Built in target (φ30mm-L660mm)•Operation current 250 kAmp
•Thermal load total 14.4 kJ/pulse (6.6 kW)(Joule’s heat) 12 kJ/pulse, (incident beam) 2.4 kJ/pulse•Water spray cooling on target and inner conductor (4x6=24 nozzles, 300kPa)•For minimize π absorption: Aluminum alloy conductor (A6061)

1.05°decline

Built-in production target (φ30mm)

NBI 2002
14-19 MARCH, 2002

Inner conductor and Target

mm066-Lmm30Φ
etrgaT

Inner conductor

current•Target rod, thin wall cylinder, tail cone
•Pulse current passes through on the target.
Æ Conductive target• Aluminum A6061, φ30mm-L660mm, ～1.67ｘλI• Joule heat 12kJ/pulse• Spray cooling ～Heat transfer rate 1100W/m2・K• T average ～60℃、⊿T ～15℃

NBI 2002
14-19 MARCH, 2002

Second Horn

•Length 2.72 m, Outer diameter 1.52m•Large acceptance•Conical inner conductor: thickness 3mm, welding joint•The inner conductor was assembled in the center within a accuracy of ±3mm.
•For minimize π absorption: Aluminum alloy conductor (A6061)•Water spray cooling on target and inner conductor

Φ1.52mΦ0.6m

2.72 mto SK

NBI 2002
14-19 MARCH, 2002

Neutrino flux with Horn current
Azimuthal magnetic field

Magnetic field on the surface of a target
61.2
1.12

1.1

Magnetic field [Tesla]

Relative neutrino yield

1.00
0.96

Nov. 99-Jul. 00 (φ30target, 250kA)

1.07

1.05

1.0

1.00

0.94

0.90

0.9
0.85

0.85

0.80

0.8

φ20 Target
φ25 Target
φ30 Target

0.74

0.7-Jun. 99 (φ20target, 250kA)

5432

10.6

0150

175

200

225

1st Horn current [kA]

25027505

10Radius from beam axis [cm]The magnetic field on the surface of a target is strengthened.
Æ Neutrino yield increases. But …

15

NBI 2002
14-19 MARCH, 2002

Yield strength N/mm2

Yield strengthRod, plate

Welding point

105

106

107 cycles

Safety factor for Target rod
φ20mm: 2.5 → 1.0 (1E7 excitations)
φ25mm: 3.9 → 1.5
φ30mm: 5.7 → 2.2
Target rod is thin.
A risk of breaking down during operation also increases.

NBI 2002
14-19 MARCH, 2002

Bending & Vibration

Fixed end

Fixed end
0Bend [m- 0 .1
- 0 .2- 0 .3- 0 .4φ２０
φ２５φ３０- 0 .5- 0 .6- 0 .7- 0 .8
0500

1000

1500

2000

2500

Po sitio n

Bending displacement δ(mm)=0.24, 0.48, 0.67
Measured frequency spectrum (FFT);
195, 437, 928, 1572, 2188 Hz, ・・・Longitudinal frequency : f n =n4L

Eg
, f 1 = 1673 Hzρ

Twist frequency :fn =n4LGg, f 1 = 1027 HzρBending frequency :fn =1 αn2π L22EIg, f 1 = 207 Hz
ρCalculation:
Excitation pulse =195.3 Hz
Longitudinal=1673, 3346, 5019,…
Twist=1027, 2055, 3082,…
Bending= 207, 827, 1861,…

NBI 2002
14-19 MARCH, 2002

The new disk for supporting innerconductor firmlycenter•

Flat –t 28mm

Spring constant up––Flat 8 ribs disk = 30 μm/kgf
New parabolic disk= 9 μm/kgf

Parabolic –t 58mm
0.30

Test parts

Deflection ［ｍｍ］

６ ribs
８ ribs0.25

Flat 6 ribs cap

parabolic cap
６ ribs (back side）

0.20

8 ribs (back side）
parabolic cap (back side)

Flat 8 ribs cap

0.15
0.10
0.05

parabolic

0.00
01020

Load [Kgf]3040

NBI 2002
14-19 MARCH, 2002

Measurement of dumping time

Flat disk with 8 ribs

Parabolic disk with 8 ribs
Result:½ decay time constant : 96ms Æ 19ms
Dumping time was able to be suppressed.

• Un-contacting Photoelectric Sensor with laser
light beam
•Resolution 1.5μm, response time 0.15ms

NBI 2002
14-19 MARCH, 2002

Spray cooling system
Outside beam line

pH v.s. Solution rate
10000

pumpSolution rate [mg/m2・h]

1000

1001010.10.01
12345678910 1112 13 14pH

HORN1 and 2
Inside neutrino beam cave

Reservoirpump•
••
•
•
•
•

Spray pressure =300kPa
Total flow = 60 lit./min.
Floating ion: [Al(H2O)2(OH)4]pH control ≒ 7.5
Conductance ≒50μS/cm
Self healing
Corrosion ÅÆ Alumite growth
Neutralize of cooling water every
2 weeksNBI 2002
14-19 MARCH, 2002

Alumite growth••New(Silver color): Ag-coating 5~8μｍ(Black alumite growth): No coating

1 year used

NBI 2002
14-19 MARCH, 2002

Tritium accumulation
Ac c u mu lat e d Tr it iu m in c o o lin g wat e r
2000

7 .0 E+ 1 9

Protons in target

1800

5 .0 E+ 1 91600

2001 runP14 cooling water

1400
200 lit. exchange

4 .0 E+ 1 9

3 .0 E+ 1 92000 run

1200
1000
800
600

2 .0 E+ 1 91999 run

400

1 .0 E+ 1 9
200
0 .0 E+ 0 0
2001/10

2001/08

2001/06

2001/04

2001/02

2000/12

2000/10

2000/08

2000/06

2000/04

2000/02

1999/12

1999/101999/08

1999/06

1999/040
1999/02

A ccumul a ted Protons

Horn and Target

Tri ti um Dens i ty [Bq/cc]

6 .0 E+ 1 9Dirty cooling water=270 liter
Major isotope products
H-3, Be-7, Na-22, V-48,
Mn-52, Mn-54, Co-56,Co-57, Co-58, Zn-65, Y-88,
Tritium density=1633 Bq / cc
(2.96E+19 incident protons)
Eliminator: Ion Exchange Resin(AMBERLITE)
IR120 Na (cation)
IRA410 Cl (anion)

Eliminator unit

Reservoir,
Pump unitEffect of Ion exchange resin eliminatorRadioactivity concentration(Bq/cc)
IsotopeH-3Be-7
Na-22
Sc-46
Mn-52
Mn-54
Co-56
Co-57
Co-58
Fe-59
Co-60
Zn-65
Se-75
Rb-83
Rb-84
Y-88
Zr-88
Tc-95m
Ag-105

Half-life

12.3 y53.3 d2.6 y83.8 d6.0 d312.1 d77.2 d271.7 d70.9 d44.5 d5.3 y244.3 d119.8 d86.2 h32.8 d106.7 d83.4 d61.0 d41.3 dbeforeafter

9.40e+2
1.15e+2
9.85e-1
7.46e-1
3.11e+01.87e+01.74e+02.46e+08.49e+01.49e-1
2.47e-1
3.53e-1
1.69e-1
1.42e+02.11e-1
2.78e+03.94e-1
2.15e-1
4.34e-1

9.89e+2
1.17e-1
1.44e-3
8.23e-3
no detectno detect
4.47e-3
7.20e-4
no detectno detectno detectno detect
3.04e-3
no detectno detect
1.36e-3
8.65e-3
no detect
1.42e-2

removal rate%•K2K experiment 10Jan,2001 Æ12 Jul,2001 (Incident protons=2.82e+19)•Dirty cooling water 270 liter•Most radioactive isotopes are removable. Tritium can not be remove.

--100
100
99
100
100
100
100
100
100
100
100
98
100
100
100
98
10097

NBI 2002
14-19 MARCH, 2002

NBI 2002
14-19 MARCH, 2002

Under durability-test
1.2E+07
1st Horn(#07）

1.0E+07

11 million excitations

1st
1st
1st

第１－７号機
第２―３号機

1st Horn(#03->#05）
2nd Horn（#01）

8.0E+06

2nd Horn（#02）
2nd Horn（#03）
1st

第２―２号
機

6.0E+06
第１－４号機
φ３０

第２－１号機

4.0E+06
Run1999

第１－３号機
φ２５

第１－５号機（3号機改造版）

Run2001

Run2000

2.0E+06
第１－２号機
φ２０

第１－６号機
パラボラ端板型

第1―8号機'99/02'99/03'99/04'99/05'99/06'99/07'99/08'99/09'99/10'99/11'99/12'00/01'00/02'00/03'00/04'00/05'00/06'00/07'00/08'00/09'00/10'00/11'00/12'01/01'01/02'01/03'01/04'01/05'01/06'01/07'01/08'01/09'01/10'01/11'01/12'02/01'02/02'02/03'02/04'02/05'02/06'02/07'02/08'02/090.0E+00

NBI 2002
14-19 MARCH, 2002

Summary••••

Mechanical failure has not happened at all since lastyear.
End cap modification was very successful.
However there is still an indefinite failure in long-term
operation.
pH control in a cooling water succeeded and advance ofcorrosion was suppressed.
The result of a durable test reached to 1.1x107
excitations. (now running)