Magnet Issues,Circumference Drift
Mika Masuzawa(KEKB Magnet Group)Contents
1. Magnet Issues (wiggler magnet)
2. Tunnel Level Changes
3. Circumference Drift

1.
Magnet Issues(K. Egawa, M. Masuzawa)
We had no major problems except:
2 wiggler magnets had layer short problems, one in
the spring of 2001 and the other one in May 2002.
w Temporarily bypassed a pair of wiggler magnets.
w (There are 76 pairs of wiggler magnets in the LER)
w Replaced them with spare coils during the following
shutdown periods.

1. Magnet IssuesSymptoms (1)wHorizontal orbit distortion appeared.
wAn error-kick analysis pointed to a wiggler magnet.

1. Magnet Issues

Symptoms (2)V̲coil(v) RURDLU

LD

BW1OLP̲30

2.51313.01503.03323.0380

BW1OLP̲29

3.00363.0025

DC Voltage across one coil was lower thanthe others, indicating a layer short.

A pair of wiggler magnets bypassed.

1. Magnet Issues

Impulse test at the manufacturer
Normal coil

Layer shorted coilwThey removed the insulating materials after
the impulse test to searchfor burnt spots but did not find any.
wThe investigation into the location and thecauses of the problem isstill continuing.

2. Tunnel Level Changes(R. Sugahara,Y. Ohsawa)
w The level markers on the tunnel wall have beensurveyed 6 times since 1996.
w
w
w
w
w
w

1st survey: June.1996
2nd survey: Aug.1997
3rd survey: Feb.1998
4th survey: Oct.1998
5th survey: Jul.2001
6th survey: Aug.2002

w The results of these surveys are summarized.

2. Tunnel Level Changes
IP(Tsukuba)
S=0Tunnel Level Changes (blue line) duringtheFeb-Jun 96
KEKB Marker Level
9 years of TRISTAN operation. Aug 97

Counter-clockwiseOho
5Nikko0TRISTAN was opearated for 9 years: Nov. '86 - Dec. '95

-5-10

Fuji

Oho

Tsukuba

▼▼▼▼▼

0750

1500

2250

3000

TsukubaNikko-15-20Level (mm)

Fuji

S (m)

2. Tunnel Level Changes
Aug'97-Jun'96
Feb'98-Jun'96
Oct'98-Jun'96

KEKB : Level Drift for Beam Level MarkersTunnel
Level Changes since June 96
for the Period Jul. '96 - Aug. '02

Jul'01-Jun'96-10Fuji

Oho

Tsukuba▼▼▼▼▼075015002250

3000

TsukubaNikko-20-15

Level (mm)-505Aug'02-Jun'96

S (m)(1)Not uniform(2)Largest drift between Fuji and Oho (south tunnel), 2.5mm/year2. Tunnel Level Changes
Aug'97-Jun'96
Feb'98-Aug'97
Oct'98-Feb'98

KEKB Beamper
Levelyear
Markersfor each survey interval
Level Changes
Oct'98-Feb'98
Level Change in a Year

▼

▼▼

▼

▼

0750

1500

2250

3000

Tsukuba

TsukubaJul.’01~Aug.’02
Oho-6

Oct.’98~Jul.’01

Fuji-4Feb.’98~Oct.’98

Nikko-2Aug.’97~Feb.’98-8

20Jun.’96~Aug.’97-12-10

Level Change (mm/Year)

Aug'02-Jul'01

for the Period Jul. '96 - Aug. '02

S (m)Stable period, which corresponds
to the KEKB commissioning periods.

2. Tunnel Level Changes: Summary
w The south tunnel has been sinking with respect
to the IP.
•(a)~4mm/year during the construction and in thesummer of 2002.
•No tunnel air temperature control.
•(b)Very stable during the KEKB commissioning.
•Tunnel air temp. was kept constant within ~ +/-1℃.
w Why south tunnel??
à Wellà Heavier (more likely?)2. Tunnel Level Changes: Summary
North Tunnel
Nikko
Exp.HallWest Tunnel

TsukubaExp.HallIP
East Tunnel

The south tunnel section is moreOhoheavily built up.
Fuji
South Tunnel Exp.HallExp.Hall
As it goes through cycles of expansion
and contraction, it loses its grip on thesurrounding sub-soil?

3 wells
The ground retains a large amountof water, which is pumped up at
the rate of several hundred tons/day.

3. Circumference Drift(H. Koiso, K. Oide, R. Sugahara, N. Yamamoto,
M. Yoshioka, M. Masuzawa)3-1. Overview

Chicane magnetsKEKB is a double ring collider

LER (3.5 GeV)

Crab Cavities(planning)

HER (8 GeV)IPTRISTAN
tunnel

KEKB
B-Factory

Four experimental buildings:
2 stories above ground, 4 stories belowground. The basement floors(16m below GL,diluvial clay strarum) are built on pilefoundations, the piles extending to 40m
below GL (gravelly layer).

BeamTransport
Lines

e+ Linac(3.5 GeV)e+ target

Four arc sections:Founded on gravelly diluvial layer~12m below the GL.

Four straight sections:
Built on pile foundations.
e- J-Linac(8 GeV)
J-Arc

There are expansion joints every 50-60 min the arc and straight sections.

3-1. Overview
KEKB tunnel cross section

80 cm concrete

3-2. Circumference Correction
Methods
Measurement and correction of l∆P ∑i x i xi
=2P0
∑i xi

∆l =∆P⋅⋅ C0
P0

Design dispersion

Design circumference

Momentum compaction factor ~3.4e-04

3-2. Circumference Correction
Tools
LER– By changing the strength of the chicane magnets : 4 sets ofbending magnets placed on both sides of the Nikko/Ohowiggler sections. The circumference correction system has
been incorporated in the ‘CCC’(Continuous Closed orbitCorrection, every 20-30 seconds).
HER & LER
– By changing the RF frequency. RF phase can be locked orunlocked. When unlocked, CCC changes the RF frequency.

Circumference adjustment with chicane
magnets (LER)

4 bending ‘chicane’
magnets

3-3. Analysis Results
Data loggedü Circumference–Chicane magnet strength–RF frequency

Well controlled

ü Environmental variables– Temperature : tunnel air, outside air, building roof,
ceiling space, magnet cooling water, etc.
– Well depth– Atmospheric pressure
Newly added from Jan. 2003
Underground temperature,more sensors in the tunnel…

Tunnel air temperature(At one location in the tunnel)
in October 2002
The tunnel air temperature is maintained at 24 +/- 1℃.

+/- 1 degree3-3. Analysis Results
Spring run: environmental variables

3-3.Analysis results
Daily highest/lowest temp. and circumference

3mm/3000m/25℃=1ppm/25℃∆circumference and outside air temp. is correlated, with wide spread.
The wide spread might indicate some time lag between the two variables.

3-3.Analysis results
Spring run: environmental variables

Semi-diurnal tidal effect onü Atmospheric pressure
Õ1hPa
ü Well depth Õ50µm

Circumference Spectrum analysis~15µm in amplitude~10µm

Spring8 (~1500m) also sees the tidal effects.
40µm peak to peak when largest.

3-3. Analysis Results
Fall run: Typhoon !!

KEKTyphoon 21 hit the area on 10/1/2002

24 hour period

24 hour period

wThe circumference expanded ~200 µm (an order of magnitudelarger than tidal expansion).
wPressure or water level??Longer term trend plots of atmospheric pressure,well depth and circumference
1 month period

fakeIt could be argued that the circumference expanded because of the uprising of thewater level on Oct.1st. The water level went up by ~0.5cm after the Typhoon andstayed high. If the water level is the main source for the expansion, we should see
a similar trend in ∆circumference trend plot, but we do not.

3-4. Circumference Drift: Summaryu Tidal effects have been observed in circumference variations at KEKB.
Lunar and solar semi-diurnal tidal effects have been clearly distinguished.
u The diurnal component observed in the circumference variation is several
times larger than the expected diurnal tidal effect. The outside airtemperature might be the main source of the enhancement.
u A long-term drift in circumference has also been observed. This drift shows
more correlation with the outside air temperature than with otherobserved environmental variables.
u The circumference temporarily expanded by ~200 m when Typhoon 21 hit
the area. The expansion coincides with the corresponding rapid
atmospheric pressure drop.
u Further analysis is required to quantify the contribution of eachenvironmental variable on the expansion/contraction of the circumferenceof the rings.

No significant peaks in the luminosity spectrum
observed

Simple modelU = gKbf ( ) cos[ ( ,t )]3 m a3
K=a = 53.7 cm
2 M r3
U' = U × (1+ k )1× U'g1∆ // = l × × U'g
1f ( ) = sin 2 = 0.327 @ = 90 − 36 = 54o2∆⊥ = 0.610 × 53.7 × 0.908 × 0.327 × 1.281 ~ 12(cm)∆⊥ = h ×

Displacement12(cm)× 3( km) ~ 60 m
6370(km)

For pressure drop,∆p=40hPa∆⊥ = 0.610 × 40cm × 1.281 ~ 31( cm)
31( cm)× 3( km) ~ 150 m
6370(km)(40cm if acted upon water)

Jan.25~Feb.8