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Document Number
xxxxx
Project Name
Spoke Cryomodule
Date
29015-05-31
Revision
Draft
Technical Specifications of the Spoke Cryomodules
Authors
Reviewers
Approver
Name
Sebastien Bousson
Affiliation
IPNO
Document Number
ESS-xxxx
Document Name
Technical Specification of the Spoke Cryomodules
Date
2015-05-31
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Document Number
ESS-xxxx
Document Name
Technical Specification of the Spoke Cryomodules
Date
2015-05-31
1.
BACKGROUND
The European Spallation Source is a Partnership of 17 European Nations committed to the
goal of collectively building and operating the world's leading facility for research by use of
neutrons. ESS will be a high-power spallation source dedicated for scientific investigations of
the molecular building blocks of matter. The facility will be constructed in Lund, in the
southwest of Sweden. Its first proton beam to a solid, rotating tungsten target will be
delivered in 2019. The target will in turn generate neutrons for delivery to an initial suite of 7
neutron scattering research instruments. ESS will reach its full design specification in 2025,
with a suite of 22 research instruments. The machine will continue to serve the European
neutron research community until 2065.
As an accelerator-driven neutron source, ESS will use a linear accelerator (linac) to create a
high-energy proton beam. The superconducting portion of the linac will contain 146
superconducting radiofrequency cavities immersed in liquid helium at a nominal temperature
of 2 K. The first superconducting section will consist of 13 spoke cryomodules, each with two
double spoke cavities. This section will be followed by two sections of elliptical cavities,
called medium-beta and high-beta sections, the beta number referring to the ratio of the
proton speed to the speed of light. These two sections will contain 9 and 21 elliptical cavity
cryomodules respectively, with 4 cavities per each module. However, there is a possibility to
install additional 14 high-beta cryomodules as a design contingency.
This technical specification defines the detailed tasks and requirements for the procurement,
manufacturing, preparation and parts testing, assembly and transport of the spoke
cryomodules constituting the ESS Spoke Linac.
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Document Number
ESS-xxxx
Document Name
Technical Specification of the Spoke Cryomodules
Date
2015-05-31
2.
DETAILED SCOPE OF WORK FOR THE SPOKE CRYOMODULES
Several sub-tasks (also called Work Unit, WU) are required to achieve the completion of 13
operational spoke cryomodules. They include:
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2.1
A design adjustment phase in order to integrate potential required changes of the
spoke cryomodule design with respect to the achieved design issued from the 20102016 Fr/Sw collaboration agreement.
Construction of spoke cavities, couplers, tuners and cryostat components in order to
complete 13 operating cryomodules
Preparation, testing and conditioning of all cavities and power couplers prior to
cryomodule assembly
Preparation and assembly of 13 spoke cryomodules
Transport of all assembled cryomodules to the high power test station at Uppsala
University
Participation to the cryomodules high power test at Uppsala
Participation to the installation of the first spoke cryomodule in the ESS linac tunnel
Design Adjustments
During the spoke cryomodule prototyping phase (work included in the 2010-2016 Fr/Sw
collaboration agreement), a complete spoke cryomodule will be tested at high power in
Uppsala. The prototype test results, together with the experience gained on its assembly and
operation might lead to a potential design improvement, either on the cryomodule
components, on the assembly tooling, or even on the preparation and assembly procedures.
This WU integrates the following tasks:
 Design adjustments (if required) on cavity, power coupler, cold tuning system,
cryomodule part, tooling, as well as cryomodule assembly or cavity/coupler
preparation procedure improvement.
2.2
Procurement
CNRS shall procure all the necessary components and systems to be able to produce 13
complete and operational spoke cryomodules. As no spare parts are required by ESS, CNRS
will procure in particular:
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Niobium raw material to manufacture 26 cavities
26 double spoke cavities (352 MHz, beta=0.5) made in bulk niobium
26 power couplers and their associated doorknob transitions
26 cold tuning systems, each integrating a stepper motor and 2 stacks of piezo
actuators
13 cryomodule vacuum vessels and their associated thermal screens, internal cryopiping, instrumentations
13 cryomodule supports
The procurement phase for each component should include the following tasks:
 Specifications for components fabrication
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Document Number
ESS-xxxx
Document Name
Technical Specification of the Spoke Cryomodules
Date
2015-05-31
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2.3
Call for tender and appropriate vendor selection process
Fabrication follow-up, adjustment at intermediate steps (for instance, frequency
adjustments for the cavities)
Acceptance tests (dimension control, leak tests, overall manufacturing quality)
Cavity preparation and testing
The superconducting spoke cavities require preparation and tests prior to their installation in
the cryomodules. Cavity preparation consists in specific cleaning, hydrogen degassing at
600°C, chemical etching (buffered chemical polishing with FNP acid), ultra pure high
pressure rinsing and clean room assembly.
After preparation, the cavities should be individually qualified for acceptance by a test in
vertical cryostat at 2K. A test report for each cavity will be delivered to ESS.
2.4
Power coupler preparation and testing
The power couplers require specific preparation and tests prior to their assembly on the
cavities and their installation in the cryomodules. Power coupler preparation consists in
specific cleaning, ultra-pure water rinsing, and clean room assembly.
After preparation, the power coupler should be RF conditioned at warm temperature and the
nominal RF power on a dedicated test bench. This same test is also used as qualification test
of a power coupler assembly. A test report for each power coupler will be delivered to ESS.
2.5
Cold Tuning System (CTS) preparation and testing
The cold tuning systems parts should be assembled and individually tested (operated) at
room temperature before being mounted on a cavity.
2.6
Spoke Cryomodules Assembly
Each of the 13 spoke cryomodules is assembled in 2 steps. First, the cavity string (2 cavities
equipped with their power coupler) is prepared and assembled inside a clean room, sealed,
and leak checked. Then, outside the clean room, the cavity string is inserted inside the
vacuum vessel, and the whole cryomodule is being assembled, and equipped with all
instrumentation.
2.7
Spoke Cryomodules Transport
After the assembly, each cryomodule will be transported to the high power 352 MHz test
station in Uppsala for the final validation and acceptance test. Specific transport tooling
design will be studied to perform the cryomodules shipping under the best conditions and to
minimize the associated risks of damages. The number of transportation tooling should be
sufficient to allow a cryomodule transportation between the assembly location and Uppsala
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Document Number
ESS-xxxx
Document Name
Technical Specification of the Spoke Cryomodules
Date
2015-05-31
University at a typical rate of 1 cryomodule every 1.5 month. The same tools will be also
used later on for the transportation between Uppsala and ESS.
2.8
Participation to the Spoke Cryomodules tests at high power
After assembly, each cryomodule will be tested under nominal conditions of RF excitation
and temperature for the final acceptance and performances assessment. These high power
tests will be performed at Uppsala University, by the Uppsala University team. CNRS will
participate to these tests in order to insure the proper operation of the cryomodule and to
validate the cryomodule overall performances.
For each cryomodule, a performance report will be written and submitted to ESS for the
cryomodule acceptance.
2.9
Participation to the installation of the first Spoke Cryomodules in
the ESS linac
CNRS will participate to the installation and commissioning of the first spoke cryomodule in
the ESS linac tunnel.
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