RHIC Maintenance and Upgrades

By

Sumanta Kumar NayakCollider Accelerator Department

OLAV III

Tandem Injector to be Replaced with EBIS Located in the LINAC Building

Accelerator Facility at BNL

EBIS

RHIC Vacuum System

Typical 4 of 8 Warm Sections per Sextant

1

2

34

RHIC vacuum system is divided into four regions

• The cold-bore UHV system, housed within the bore and at the interconnects of the

super conducting magnets.

• Warm-bore systems, between cryostats and within the magnets.

• Cryostat vacuum systems, serving as the guard vacuum for superconducting

magnets.

• Special experimental regions, unique vacuum material and pressure requirements

• Roughly 20% of RHIC is warm bore.  This corresponds to a total warm beam line length of approximately 700m.

• There are 46 UHV warm beam line sections separating 4K superconducting

beam line sections and beam injection in RHIC. Typical warm segments are

between 12 and 34 meters long

• Some of these warm beam lines are further segmented to allow service of

particular beam line components without disturbing adjacent components.

• Arrangement adds infrastructure cost (e.g., rf-shielded valves, controls and

cables, gauging etc.) but saves time and effort and reduces risk to the

adjacent warm space components in same beam line.

• Every year 15-20 warm beam line undergoes modifications such as

upgrading old equipments, adding new machines or modifying existing

system.

RHIC Warm Beam lines

Recent Modifications Beam Dump

• For 120 GeV 3x109 Gold ion intensity, the superconducting magnet next to

the dump was getting quenched

• It was decided to increase the elliptical beam tube thickness

• 20 numbers of Dicronite coated sleeves (each 5” length) inserted into the

tube

192” (4.8m) length elliptical beam tube (1.91”x1.75” OD)

Beam dump entry Beam dump exit

Window

Dicronite coated sleeve

Recent Modifications

Addition of Spin Flipper System

Spin flipper system

AC Dipole

DC Magnet

Ceramic tube - TiN coating going on

Plasma seen during coating

Ceramictube

Ti tube

• For last 3 years we are continuously adding

machines

• Consists 5 AC dipoles and 4 DC magnets

• Ceramic tubes are TiN coated to prevent

charge build up and suppress electron cloud

Ionization Profile MonitorOld Design

• Kapton Film, PEEK Screws

• Collector Array – Rogers 4000 Circuit

Board

• Al Honeycomb Panel – Organic Adhesive

• Bakeable to 120 0C

New Design

• Ceramic Screws, Standoffs

• Ceramic Beaded Wire

• Ceramic Board

• Stainless Welded Honeycomb

• Bakeable to 200 0C

• Vacuum improved from 10-10 to 10-11 torr

Recent Modifications

RHIC Tunnel ODH-1 to ODH-0 by Failure Monitoring Pressure Switches

• RHIC tunnel, a potentially oxygen deficiency hazard (ODH) zone during operation

• Cryostat houses the cold mass and provides insulating vacuum

• Pressure switches are installed in cryostats and would be soon coupled with

valves in the liquid helium flow line

Omega Edwards Leybold Precision Sensors

VENDOR COST FLANGE WETTED PARTS (leak rate) RANGE

MAX ALLOWABLE

PRESS ENCLOSURE ELECTRICAL

OMEGA Engineering 89

1/4" male VCR stainless steel (E-9 mbarl/s) adjustable, 1.6 to 27 " Hg 0 PSIG NEMA 4

NO/NC, 1 amp res/125VAC gold plated

Edwards Vacuum 200 KF 16 stainless steel (E-9 mbarl/s) adjustable, 30-1000 mBar 1 bar gauge IP40NO/NC, 10 amp res/125VAC,

silver plated

Leybold Vacuum 189 KF 16

EPDM (rubber) diaphragm (E-6 mbarl/s) * PTFE

coated SS fixed, 4 Torr below atm 1 atm gauge IP44NO/NC, 30 mA/28VDC, gold

plated

Precision Sensors 273

1/4" male VCR stainless steel (E-9 mbarl/s)

fixed, factory settable, 125-750 mm Hg 25 psig not rated

NO, 1 amp res/ 28 VDC gold plated

Cryostat Relief ~1.5 psig

0.4 watts required for silver contacts to break through contact oxidation. (Cherry Corp)PLC control is 6 mA at 24 VDC (0.14 Watts)

Electron Beam Ion Source (EBIS)

Internal distributed NEG Pump

Removable Electron Gun Unit

Gun Transition Vacuum Chamber

Electron Collector Vacuum Separation Stage

Electron Collector

Beam line isolation Gate

Valve

Drift tubes

E-Gun

TSP & Ion Pump

Solenoid Central Beam

tube

Central Vacuum Chamber

Electron Collector Transition Vacuum Chamber

EBIS Platform Assembly Section View

Buffer vacuum chamber

• EBIS is a new heavy ion pre-injector to RHIC

• 10-10 – 10-11 Torr vacuum required in the beam region.

• Only UHV compatible materials used – stainless steel and ceramics

• Stainless steel chambers, Inconel bellows and Conflat flanges

• All the chambers are baked at 2500 C, while the central drift tube is baked at 450oC

Transverse Coil

Copper shield

Kaowool Insulation

Coolant Tube

Firebar Heating Element

Vacuum Chamber

Support Tray

Drift Tube

HV Power Feeds

NEG Support Cage

Beam Region 10-10 - 10-11 torr

Drift Tube Chamber Vacuum Requirements

• NEG pumping in beam region

• Drift tube chamber separated from high gas loads of electron gun and electron collector by conductance of 100 L/sec

End View of Drift Chamber

Firebar and insulation to protect the superconducting tank

High voltage drift tube

Spiraled ST 707 NEG

85% transparent screen

Drift Tube Detail

Electron Beam Ion Source (EBIS)

Spiraled ST707 NEG Strip

ST 707 NEG Strip

Stochastic Cooling

Square box with removable top flange Top flange with tabs for welding allows for grinding of weld for removal

Side and end view of SC device mounted on top plate with finned heat sink used for heating during bakes and cooling during beam

operation. RF cavity plates are copper plated Aluminum, hinge open and close to alter beam aperture for tuning

Coax cables 50 Ohm, 1dB loss @9GHz must be flexible with 2.5

cm bend radius unfortunately have Teflon insulation

Helicoflex seal didn’t work at 200 0C temperature

• Every RHIC warm beam line section receives some sort form of elevated temperature process following maintenance or upgrade that required a bleed-up.

• Approximately 15 – 20 RHIC warm space regions are serviced during each shutdown.

• The upgrade/maintenance process requires bleed-up, some degree of deconstruction, followed by new component installation reconstruction, including survey and vacuum, followed by a vacuum bake out and vacuum commissioning.

• Anywhere from 10 to 30 kW of power is required to bake out a RHIC warm section.  Power is distributed to the beam line according to component and thermal mass resulting in anywhere from 12 to 40 zones per bake out.

• Every warm section is different.  A portable bake out power distribution and control system features the flexibility needed to adjust to these differences.

RHIC Vacuum Bake outGeneral System Requirements

BNL C-AD Vacuum Bake out

Controls CartPower Distribution Cart

24 Zone Bake out System

Front: 24 zone PID Controllers divided into 3 groups of 8, top level system controls, Setup Computer and UPS

Rear: 3 multiwire connectors for 8 T/Cs each and 3 multiwire connectors for 8 associated output signals to SCRs to control heater power, and 3 Dry contact Interlocks.

480V Transformer with 208 3Ø Output & Disconnect

Rear: 3 208V 3Ø Outlets to Mobile SCR Racks (NOT shown) 8 SCR zones for each SCR rack, 24 Total

• The portable bakeout system is integrated into the warm section following installation, pumpdown and leak check of the beamline.  Thermocouples and heater jackets are installed, routed and terminated into the bakeout system.

• This has traditionally been a time consuming effort, but is improving since funding over the years have allowed for the purchase of more heater jackets eliminating the need to relocate and reinstall jackets.

• A typical warm space is prepped for bake out in one week or less.  Bake out and commissioning is conducted over the course of another week.

• At peak times (near the end of shutdowns) when most new devices are finally pressed into service, 3 bakeouts are often in progress simultaneously.

• Most bake outs are conducted exclusively with heater jackets constructed of nickel-chrome resistance wire and fiberglass insulation. However there are a few areas that require alternate methods of heating the beamline.  Some RF cavities are heated by passing heated water through the cooling passages of the cavities.  Other regions pass heated dewar nitrogen through the beamline, a process referred to as hot nitrogen scrubbing.

RHIC Vacuum Bake out Process Overview

0 10 20 30 40 50 60 70 80 900

50

100

150

200

250

300

Programmed Temperature Profile for RHIC Bake out and NEG Activation

Time (hr)

Tem

per

atu

re (

C)

~ 48hr DwellSTD Equipment

Degas TSP & RGA Bump Ion Pumps & Gauges

TSP sublime(2hr dwell)

2nd degas TSPs(2 hr dwell)*

SIP on, TMP off

2-4 hr NEGActivation

Standard EquipmentNEG Coated Beam tube

NEG Film H2, N2 Degas ~1 hr

*Ideal 2nd Degas time. However, 2nd degas usually performed by end of STD Equipment dwell due to normal 8-4:30 pm work shift constraint.

8am - 4:30pm

RHIC Warm Space Bake out Zone Schematic & Execution

Hot Water Bake outMotivation

• Blankets were very expensive at that time

• Space restrictions

• Flow lines for hot water are available

Flow lines originally made for cooling the cavity

Hot water bake out in processRF cavity

Mokon Duratherm HTP circulating water

temperature control system

Hot Water Bake out Hot Water used at:

• CERN LEP cavities. (150°C)- *CERN SPS cavities baked to 135°C with electric heating jackets.

• SLAC B-factory vacuum chambers.• KEK Tristan APS cavities. (145°C)• PLS storage ring (Korea). (150°C)• APS vacuum chambers at ANL. (150°C)

Proposed Equipment

• Mokon Duratherm HTP circulating water temperature control system.

- These units are primarily used in the extruded plastics industry.

- Fed by existing water system for supply.

- Supply pressure 100psig and temperature is 150 0C.

- System integrated into existing bakeout cart which will be heating other

components with conventional electric jackets.

- Unit shares the same Eurotherm PID controller for ease of integration.

• Every year the vacuum system in RHIC goes through modifications and upgrades.

• All the work has to be completed during RHIC shutdown period (July-Nov/Dec)

• Design, planning, procurement and fabrication are carried during RHIC operation

• Bakeout of each section is very time consuming process.

• Portable bakeout systems offer flexibility and minimize infrastructure costs.

• Most bake outs are exclusively conventional.

• Set-up times improve each year as operational funds have added heater jackets to inventory allowing more permanent coverage of beamline components.

• The latter portion of shutdowns remain a challenge as devices scheduled for installation throughout the shutdown experience delays resulting in manpower loading strain and resource limitations.

• While careful coordination and planning prior to shutdowns helps limit these situations. Even more coordination is needed late in shutdowns to avoid accelerator start-up delays.

Summary