Interac(onRegion
Mechanicals
Overview
20th KEKB Accelerator Review Commi=ee
KEK, 23‐25 February 2015
Ken‐ichi Kanazawafor
KEKB Vacuum GroupIR Technical Mee(ng Member
IR Installa(on Mee(ng Member
SVD/IR Mechanics Mee(ng Member

Contents• Addressing the last commi=ee report• Prepara(on toward Phase 1• Issues for Phase 2 and later• Summary2

19th KEKB Accelerator Review Commi=ee Report

Execu(ve summary
Recommenda(ons:4) The SuperKEKB/Belle II interac(on region IR is extremely complex andthe Commi=ee recommends con(nued a=en(on to the issues of the beam‐beaminterac(on, beam life(me, superconduc(ng magnets, vacuum pressure,backgrounds, assembly, and machine detector interfaces.
Reply:
We con(nue our eﬀorts.

3

19th KEKB Accelerator Review Commi=ee Report

Findings and comments (Pressure of IR)
Concerns:
There is no vacuum pumping over +/‐4 m as agreed to by the Belle II detector as there is nospace for internal or external pumps. The poten(al use of a vacuum simula(on code isrecommended to predict the vacuum proﬁle in the IR region. This would be a good task for ayoung vacuum person leading to an op(mized choice of vacuum pumping outside the IR beyond
4 m. The calcula(on of the pressure proﬁle during the scrubbing phase proﬁle is also very
important to predict the validity of the concrete shielding. The simula(on should take into
account also methane degassing: the nearest pump to the interac(on point has a very low
pumping speed for CH4. The indica(on that ‘the average pressure in the IR region will be 10‐6 Paor higher’ should be further inves(gated in detail with the hope of understanding the maximumpressure and making it as low as possible and consistent with Belle II opera(on. (See the nextslide)
Recommenda(on:New calcula(ons of the expected vacuum pressures in the IR should be completed including
the new chamber geometry, surfaces, and beam condi(ons.
Reply:
I agree the importance to inves(gate a pressure proﬁle near IP. I made contact with R.
Kersevan and M. Ady. I also a=ended the Molﬂow seminar by M. Ady held at KEK. We agreed tostudy somewhat simpliﬁed IR model. However, I have not yet prepared necessary data, becauseof the complexity of IR geometry. I think we should get some results un(l Phase 2 (not an urgent4issue).

Vacuum system of IRNo vacuum
pumps in thisregion

19th KEKB Accelerator Review, K. Kanazawa

519th KEKB Accelerator Review Commi=ee Report

Findings and comments (Electron cloud in IR)
Concerns:
In the present design, there is no TiN coa(ng in the IR region. It is not clear if
scrubbing would be as eﬃcient as in the rest of the accelerator. It is also not clear
where solenoids could be installed in case electron cloud appeared in the IR chambers.
Reply:For Phase 1, all positron beam pipes are
TiN coated. Since the stored current at
Phase 1 is 0.5 – 1 A. This is suﬃcient.
For later Phases, there is always a certain
kind of magne(c ﬁelds. If we see a solenoidcomponent, it is strong enough to suppress
the cloud. However, simula(on under thereal complicated ﬁeld pa=ern will benecessary to es(mate a real density of thecloud. The eﬀect of the cloud in a large beta‐func(on region is large.

H. Yamaoka
619th KEKB Accelerator Review Commi=ee Report

Findings and comments (RVC)
Concerns:
A produc(ve collabora(on has been made with a group at DESY to explore the“remote vacuum connec(on”. A good solu(on is not yet deﬁned. It is not clear when adecision will be taken and on which criteria.
Recommenda(on:Perform laboratory tests on the reliability of the “remote vacuum chamberconnec(on” under vacuum condi(ons.
Reply:AIM with RVC was approved at 18th B2GM (18‐21 June 2014).
For more on RVC, see later slides.

719th KEKB Accelerator Review Commi=ee Report

Findings and comments (Residual ac(va(on)Concerns:
The Radia(on Control Group should evaluate whether the larger backgrounds in theIR with SuperKEKB will lead to signiﬁcant residual ac(va(on of the IR vacuumchambers. A possible consequence could be that if the IR region vacuum chambers
need to be worked on, they may be too ac(vated to quickly ini(ate a repair.

Reply:For an electron collider, residual ac(va(on around IP is not serious compared tohadron colliders. Rather, radia(on damage on detector components is an importantissue. Radia(on dose on the detector components is repeatedly es(mated along withthe es(ma(on of beam background.

8

19th KEKB Accelerator Review Commi=ee ReportFindings and comments (QCS beam pipes)
Recommenda(ons:Finalize the vacuum chamber designs for Phase II within 4 m of the IP and proceedwith engineering.
Reply:See later slides.

9Prepara(on for Phase 1 (early 2016)
New
shieldwall
(Sep.
2015)

Gate shield(Oct.‐Nov. 2015)

LABM: July
Beast 2: September?

Newshieldwall(Sep.
2015)

All beam pipes will be installed and connected (ll the end of June, and will be pumped down.

IP shield(Oct.‐Nov. 2015)10

Prepara(on for Phase 1

Reinforcement of IP1 chamber
The central chamber for Phase 1 IR, IP1, developed a crack on a weld
seam during prepara(on for TiN coa(ng (K. Shibata).
The chamber will be re‐welded and ver(cal ﬁns and side bars will bea=ached for reinforcement. The work will complete before 19 June 2015.
Positron path

Side barVer(cal ﬁnPosi(on of the crack11

Issues toward Phase 2 and later• QCS issues, fabrica(on, ﬁeld measurement,and cables (N. Ohuchi and Magnet group)• IP chamber• RVC (Remote Vacuum Connec(on)• Beam pipes for QCS

12

Issues toward Phase 2 and later

IP chamber

The IP chamber for Phase 2 is completed. However, without feedback from Phase 2experiences, the next chamber for Phase 3 must be fabricated.

S. Tanaka

Early 2018: The installa(on of VXD starts.
Early 2017: The assembly of VXD and its cosmic‐ray test must start.
May 2017: Phase 2 run starts.
Therefore the next IP chamber mast be produced before Phase 2. Already,machining of Ta part was over. Comments on the present design are welcome.
13

Issues toward Phase 2 and later

IP chamber: Design feature
HIP = Hot IsostaticPressing

Only taper parts are exposed
to direct synchrotron
radiation from the last bend.
Taper: to reduce the number ofphotons entering into thecentral part
+Ridges: to keep the directionof scattered photons awayfrom Be~10 µm(~10 µm)~10 µmNegligible trap of HOM atthe central part.
14

Issues toward Phase 2 and later

IP chamber :Central part
Ti

Ti

BeTi

TiBe•The central straight partconsists of double tube.
Paraffin runs between them.
•Outer Be: 0.4 mm thick•Inner Be: 0.6 mm thick•Gap: 1 mm
•The connection between
double tubes is done by Ti-TiEBW.

15

Issues toward Phase 2 and later

IP chamber: Underlying studies• Related works performed for the design and production of IPchamber– Cooling test of the central part using a dummy model– Mechanical analysis– Impedance estimation– Measurement of tip-scattering of photon on a ridge– Photon-induced desorption measurement of Au coat, Cu, and Ta– Estimation of SR background inside chamber– DC sputter coating test
– HIP and welding test under various conditions• Ref.
K. Kanazawa, The 18th KEKB Accelerator Review Committee, KEK, 4-6 March 2013,
K. Kanazawa, 7th Belle PAC, 10 -11 March 2013, KEK16

Issues toward Phase 2 and later

RVC : Where to use• IP chamber is supported by VXD frame.
Both sides of IP chamber are fixed to the VXD frametransversally and are free longitudinally.

• VXD is supported by CDC.

• Connection flanges forvacuum chambers.

The R-side of VXD is aligned transversally and isfree longitudinally.
The L-side of VXD is fixed to CDC.

• QCS cryostats can move out.

Top view

Ler‐hand side(Backward)

Some work spaces toaccess flanges.
It will be possible to
make use of thesespaces.

Right‐hand side(Forward)

CDC

Little work space toaccess flanges.
It is impossible to connect
flanges by hands in thisconfiguration.
17

Issues toward Phase 2 and later

RVC: Bellows unit between IP chamber and QCS
CrCu

BPM pick-up

CrCu

QCS
sideCooling channel

Bellows unit with aconventional RF-bridge.
A comb-type structure cannot
give a sufficient flexibility fora small diameter.

18

Picture 14 -19: How RVC works.

Two bellows units are attached to a single
flange with a retainer.

Karsten Gadow | KEK&DESY EVO Meeting | 01.06.2012 | Page 19

Picture 15

These components rotate to catchthe bellows flange.

Karsten Gadow | KEK&DESY EVO Meeting | 01.06.2012 | Page 20

Picture 16

Karsten Gadow | KEK&DESY EVO Meeting | 01.06.2012 | Page 21

Picture 17

Cylinderfor dry N2(about 50bar)
Thesecomponents
shift to press
the bellows
flange to thecryostat.

Karsten Gadow | KEK&DESY EVO Meeting | 01.06.2012 | Page 22

Picture 18

This large
screw nut
turns to lockthemechanism.

Karsten Gadow | KEK&DESY EVO Meeting | 01.06.2012 | Page 23

Picture 19

Karsten Gadow | KEK&DESY EVO Meeting | 01.06.2012 | Page 24

Issues toward Phase 2 and later

RVC: Approval

AIM with RVC was approved at 18th B2GM (18‐21 June 2014).
• The mock‐up of RVC was transported from DESY to KEK.
• The vacuum (ghtness over several months (since November2013) was veriﬁed. The demonstra(on included the opening
and closing of the vacuum connec(on. Arer re‐connec(on,the vacuum (ghtness was conﬁrmed.
Emergency procedure when RVC is stuck was agreed.
• Ler‐hand side: Make a space for hand access by removingsome electronics of CDC, and detach RVC from QCSL.
• Right‐hand side: Pull out VXD with QCSR.
For the later deployment of the RVC, a Helium pipe for leakcheck arer pipe connec(on and a guide tube for a ﬁber scopefor visual inspec(on was requested by the vacuum group.
Comments from experiences on similar components arewelcome.
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Issues toward Phase 2 and later

RVC: Boundary condi(ons (1)••••The distance of the front face of QCS is ﬁxed.
The basic shape of the front cap of QCS is ﬁxed.
The posi(on of the sealing surface between a QCS beam pipe and a bellows unit is ﬁxed.
The length of the bellows unit is ﬁxed.

The QCS‐side end of thebellows unit must be modiﬁed
to ﬁt the RVC design.

These front caps made of heavy metal and stainless steal replace theoriginal caps when RVCs are installed. The design of their front facemust be done along with the design of RVC.

26

Issues toward Phase 2 and later

RVC: Boundary condi(ons (2)K. Ackermann (MPI)The necessity of shields around the bellows unit next to IP chamber (Nakayama) is underdiscussion. Prac(cally there is li=le space for the right hand side. The issue be discussed
8‐9 May by Belle‐II Members.
27

Issues toward Phase 2 and later

RVC: scheduling2015 Now (KEK Vacuum group and Belle‐II group)• Boundary condi(ons related to the QCS cryostat is nearly ﬁxed.
• Space alloca(on around the right‐hand side RVC is s(ll under discussion. This will bediscussed 8‐9 May by Belle‐II Members.
2015 June – December (KEK and DESY)• Design of RVC (DESY)• Design of the bellows unit (KEK/DESY)• Design of the front cap of QCS (KEK/DESY)
2016 (DESY and KEK)
• Fabrica(on and Laboratory test of RVC (DESY)• Fabrica(on of the bellows unit (KEK/DESY)• Fabrica(on of the front cap of QCS (KEK/DESY)
2017 March – April (before Phase 2)(KEK and DESY)• Installa(on of RVC28Issues toward Phase 2 and later

Beam pipes for QCS

The ﬁrst design was completed for the QCSL positron pipe. Material is changed from Ta (veryexpensive) to Stainless steel. Since QCS has a thick heavy metal (W) shield around beam pipes, thischange has li=le eﬀect on detector back ground.
Four pipes will be prepared (ll March 2017.
O‐ring seal
Helium vessel
betweenbeam pipes
QC2LP
QC1LPand thecryostat.

Bellowswith O‐
ring seal

QC2LE

Beam pipe with a 4 mm thick wall, andwith water cooling channels therein

BPM

QC1LEQCSL Cryostat

Heavy metal cap replaces
the original cap arer ﬁeldmeasurement.

29

Issues toward Phase 2 and later

Beam pipes for QCS: Installa(on (1)ConceptualCenterof mass
~20 kgSlide the central part ofthe cryostat

Ductsupporttool
Without BPM
pick-ups

Based on the idea of N. Ohuchi

Pipe support

QCS
support
tool

There is no rigid connec(onbetween these bodies.
30Issues toward Phase 2 and later

Beam pipes for QCS: Installa(on (2)Attach BPM pick-ups by screws andconnect cables.

Leak check!

This installa(on work seems very delicate. In preparing assist tools, necessary
condi(ons must be discussed and be clariﬁed.

31

Issues toward Phase 2 and later

Beam pipes for QCS: Installa(on scheduleFY2015• Design of a duct support tool (Vacuum group)• Design of a QCS support tool (QCS group)• Fabrica(on of one or two beam pipes (Vacuum group)
FY2016• Fabrica(on of a duct support tool (Vacuum group)• Fabrica(on of a QCS support tool (QCS group)• Fabrica(on of remaining beam pipes (Vacuum group)2017 March ‐• Installa(on:1. Remove pipes for ﬁeld measurement from QCS
2. Replace the front cap of QCS
3. Install beam pipes
4. Install RVC
32

Summary• Prepara(on for Phase 1 is steadily in progress.
• The IP chamber for Phase 2 is completed. However, the nextchamber for Phase 3 must be prepared without feedback from
Phase 2 experiences. Any comments on the design are welcome.
• The use of RVC was approved at 18th B2GM (18‐21 June 2014) arera well‐performed demonstra(on. It is helpful to hear fromexperiences of the use of similar remote mechanism in inaccessible
condi(ons.
• The ﬁrst design was completed for the QCSL positron pipe. The costof Ta beam pipe was found quite expensive. Material is changed toStainless steel. Since QCS has a thick heavy metal (W) shield aroundbeam pipes, this change has li=le eﬀect on detector background.
• The installa(on of QCS beam pipes seems a very delicate work.
More a=en(on to the process and the prepara(on is necessary.

33