Letter-of-Intent for Test-beam Facilities at J-PARC

Spokes Person
Collaborators

Sachio Komamiya
High Energy Physics Committee ;Keisuke Fujii, Takuya Hasegawa, Seigi Iwata, Shinhong Kim, Sachio Komamiya,
Shin-ichi Kurokawa, Toshinori Mori, Kouichirou Nishikawa, Yasuhiro Okada,
Taku Yamanaka, Masanori Yamauchi
Subcommittee for LoI write up; Yoshiaki Fujii, Shoji Uno, Tetsuya Yoshida

1 Purpose and Importance of Test-beam Facilities at J-PARC
Detector technologies for high-energy experiments nowadays have become very complicated and of cuttingedge. Those technologies and devices must be tested and verified carefully at every stage: designing thedetector system, examination of test module performances, and validation of prototype detector performances.
For these purposes, test-beam programs are mandatory.
KEK-PS has been providing precious and unique opportunities of test-beam programs for 25 years. This,
however, has been determined to be shut down at the end of JFY 2004 due to the J-PARC construction. At
this occasion of the call of LoI for J-PARC experiments, we would like to propose construction of test-beamfacilities in the K-hall at the first phase, and in dedicated halls attached to the 50 (30) GeV main-ring beam line
and/or to the 3 GeV booster beam line at the second (or could be further later) phase.
KEK-PS has been providing two test-beam lines, T1 and  2, over a quarter century. They have been extremely
precious for detector development of hundreds of KEK-PS experiments, TRISTAN and KEKB experiments,and many others carried out at FNAL, BNL, SLAC, CERN, DESY etc, as well as experiments currently underconstruction such as ATLAS. So far, about 18 experiments are carried out every year on average, with total
allocated beam time of 300 shifts/year. We have not had current prosperity of the high-energy physics inJapan without them. They should also have been going to play an essential role in detector development forJLC, SuperB, and many experiments to be proposed at J-PARC such as a long-baseline neutrino oscillation
experiment and kaon super-rare-decay experiments, if not terminated. Construction of test-beam facilities
which succeed their role is of vital importance.
In addition, test-beam experiments have been very good educational programs for students. Current particle experiments are large-scaled and long time-ranged, and hence one can not participate in all steps and subsystemsof experiments. In the test-beam experiments, on the contrary, students can work on designing, construction,set-up, data-taking, analysis, and publication of the results, with actual work on all sub-detectors. This precious
experience is something which present particle experiments can not provide.
At the T1 and  2 beam lines, unseparated beams of momenta up to 4 GeV/c with momentum bite of 1% andinclusive intensity of several thousands per spill are available. These performances, together with equipments
presently provided at the T1 and  2 area, are the baseline requirements for the test-beam facilities. Thosebaseline requirements imposed to the new test-beam facilities are described in the section 2. Other optional,
but very important, requests are also described there. A summary is described in section 3.
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Requirements on the beam and the area of the test-beam facilities

The baseline of the requirements on a new test-beam facility at J-PARC is to be a specification of the  2beam line at KEK-PS. Better beam quality and facilities in the beam area, however, will also be important anddesired. In this session, requirements on the beam and the area of the test-beam facilities are described.

2.1

Beam requirements

Major requirements to the beam characteristics are summarized in Table 1. Most of the requirements are similar
to the T1/ 2 properties: one exception is the maximum beam momentum. In order to have complementaryfeatures of the test-beam facilities over the world (CERN, FNAL, etc), it is highly required that the beam
momentum should range up to 10 GeV/c. Since several users need to stop an incident beam inside theirequipments, lowest momentum is to be less than 0.5 GeV/c. Momentum bite of 1 % should be good enoughfor the most of test experiments. However in case no momentum-analyzing magnet is provided in the beam
area, better momentum bite must be available at the sacrifice of the beam intensity.
Variable beam intensity is to be a very crucial issue. Users sometimes need to have an intensity of a few
particles per spill to avoid a pile-up effect of their equipments. On the other hand, several users need to havehigh statistics in their test experiments or to study the response of their equipments under the high intensity
condition up to a thousand particles per spill. Thus user-adjustable intensity of the beam is strongly required.
Test-beam should consist of electrons/positrons, kaons, anti-protons and deuterons as well as pions and protons.
In a low momentum region below 2 GeV/c, separated beam by a DC separator will be desired to enhance thepopulation of rare species, as is provided at K2 beam-line at KEK-PS,
Table 1: Requirements to the beam properties.

momentum
momentum bite
intensity[particles/s]
particle species1)
time structure

must/indispensable
0.52 GeV/ceasily tunable
less than 1%
electrons: 110inclusive: 1100
easily tunableunseparated e Kppflat-topshould/required
up to 10 GeV/cdesiredpreferred/optional

analyzing magnet
up to 100
up to 1000
DC separator 2)

e-enriched tertiary
chopper

1. Polarity of the beam line must be easily switched, including the DC separator, to obtain both positive and negative
particles.
2. Existing at K2, and can be transfered to the new facilities.

A beam spill should have flat-top time structure to provide uniform intensity in the spill. As for the timestructure, it would be useful, in some special detector-readout schemes, to have a chopper magnet to thin out
the bunch population to make inter-pulse time longer.
It is very useful to have an option of the electron/positron-enriched tertiary beam by using a sweep magnet anda removable converter just after the primary target.
Finally the operation of the test-beam should be easy even for a novice. Users do not want to spend their short2

beam time to study the property of the beam nor to find proper beam parameters. Well-known beam parameters
should be provided by the experts and the beam control system should be designed to be convenient to theunexperienced users and to be robust against the human errors.

Table 2: Requirements to the area utilities.

number of lines
beam height
hoist:
lifting heightlifting weightarea sizes
electricity
and infrastructure
counting room

equipments

must/indispensable
11.8mshould/required3mseveral hundred kg

5.5m
30ton10m-long6m-widestabilized 100V 100A 1)

existnetwork
telephone over Japan
moving stage 2)(a few hundred kg)

UPS 100V 30A1)3-phase 200V 30A
clean ground2-groups capacity
CATV monitor

large-aperturemagnet (2T) 3)
gas Cerenkov
counter1)

desired2 (isolated)12m-long8m-widemoving stage(30ton)trackingchambers4)
momentumanalyzingmagnet5)

preferred/optional

non-magneticfloor
homeothermalwaterstrong magnet(3T)

1. Existing at  2/T1, and can be transfered to the new facilities.

2. Many moving stages up to several tons exist at KEK-PS E-hall, which are of user-properties.
They may be transfered to the new facilities.
3. Ushiwaka at  2 can be transfered to the new facilities.
4. Readout electronics should also be provided.
5. Former D5 at  2 can be transfered to the new facilities.

2.2 Area requirements
Well-maintained beam areas are inevitable to carry out test experiments efficiently. Users can concentrate on
their own equipments during short allocated beam time if utilities such as a moving stage, particle identifiers,a momentum analyzing magnet and beam tracking devices are provided as a common facility. Two or more
test-beam areas are desired in the J-PARC, which are completely separated radiation controlled areas, to carryout one test-beam program and preparation for another in parallel.
32.2.1 Size of the beam area
In order to discuss the size of the beam area, we have to assume the size of the equipments to be tested in thearea. Here we defined a maximum size and weight of the equipments to be 3.5 m and 27,000 kg, respectively,
which correspond to the size (height) and the weight of a burden to be allowed to transport on roads with regularpermission.
Beam area should have a depth of 10 m and a width of 6 m, which is needed to carry out position scan of 3.5mlong device from its center to the end. A wider width of 8 m is desired to enable the survey of the position
dependence over its full span. In order to illuminate the center of the equipments up to 3.5 m-high, the heightof the beam should be higher than 1.8 m from the floor level.
Since some equipments do not accept a residual magnetic field in the beam area, the floor of the beam area ispreferred to be non-magnetic, but to be electrically grounded.

2.2.2 Utilities in the beam area
A hoist is mandatory to install user equipments into the beam area. Capacity of the hoist should be more than
30,000 kg, which accepts the maximum weight of the equipments defined above. The head of the hoist shouldclimb up to 5.5 m to handle 3.5 m-high equipments.
Many users are to move or rotate their equipments to survey its position and angle dependence to the incident
particles. A moving stage (X, Y and rotation) is strongly required in the beam area. The capacity of the moving
stage must be at least a few hundred kg, which most of university laboratories can handle, and is desired to be
30,000 kg, the assumed maximum weight.
Several particle detectors are preferred to be provided as a common facility. A set of gas Cerenkov counters
was used as an electron identifier in the  2 beam line at the KEK-PS. Again in the J-PARC, a set of gas
Cerenkov counters will be required. Drift chambers in the test-beam area have been desired by many users.
These chambers are used to track incident particles event by event as well as to study beam profile. Past users
in the KEK-PS spent their beam time to set up drift chambers by themselves. The beam-test at the J-PARC will
become more efficient if those tracking devices are provided as a common facility together with their read-outelectronics. The trackers can also be used as a part of momentum analyzer described below.
Sometimes a user has to know precise momenta of the incident particles just in front of their equipments. A
small-gap dipole magnet is desired as a momentum analyzer. In addition to this small-gap magnet, a large-gap
magnet providing up to 2 T is strongly required in a beam area to study the response of the equipments in astrong magnetic field.
Good condition of the electricity is also important. Stabilized power supply is strongly required. Uninterrupting
power supply should also be provided. 100 V 100 A (stabilized), 100 V 30 A (uninterrupting) and 3-phase 200
V 30 A would be required to the test-beam area and the electronics hut. Clean ground should be defined inside
the beam area and in the electronics hut. It would be useful if homeothermal water is provided to keep thetemperature of detectors stable: for some devices, it is essentially important.
The electronics hut should have large capacity to accept two or more user groups simultaneously. In thehut, information such as the accelerator status and the beam intensity should be provided. A network service,sufficient IP addresses, and a few PCs which can be used for data taking/monitoring are of essential importance.
A telephone line is also indispensable which can be called directly from the outside of the J-PARC to keep
communications with user’s home institutes.
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3 Summary
In principle, LoI for construction of test-beam facilities themselves may deviate from the very purpose of LoI:
what must be called for are LoIs for test-beam programs at test-beam facilities rather than LoIs for constructionof test-beam facilities. However we dare submit an LoI for construction of test-beam facilities here since there
are no plans at present for construction of test-beam facilities.

The most important condition to the test-beam facilities at J-PARC is that at least one channel does exist
attached to the currently-postulated extraction lines in the K-hall at the first day of the operation, even though
the performances are limited. Test-beam of momentum up to 2 GeV/c with intensity of ten particles/sec
will be adequate for many test-beam programs.

Eventually we hope two extraction lines will be constructed in a dedicated test-beam hall. One beam line isfor general users with baseline requirements. We prefer to have a switching dipole-magnet at the end of thebeam line to feed the beam into two areas separated by a radiation fence, so that one user can carry out atest experiment with the beam while the next user can do a preparation without beams simultaneously. This,
however, can be a optional feature to be realized at the later phases.
Another beam line will be to provide beams with the highest momentum. Desired but not mandatory criteria,
which require expensive equipments, are to be satisfied in this line. But, if budget situation is tight, this highmomentum beam line can be realized after the construction of the low momentum beam line described above.
Another key issue for the test-beam is availability in a year. During the extraction period to the neutrino beamline, the beam may not be delivered to the K-hall. In order to realize full availability of the beam through ayear, construction of the test-beam line at 3 GeV booster area, for example, should be seriously thought out.
In case an unseparated beam can be extracted with an intensity of one or two particles per spill at the 25-Hz
repetition rate, this beam line becomes suitable for test experiments which just need to expose their equipments
to the beam. However this request exceeds the LoI on experiments at J-PARC-PS.
Finally, we hope that procedures for test-beam experiments will be fairly simple, quick, and flexible.

As a conclusion, we have to seriously recognize that there are no hadron beams in Japan during the transition
stage from KEK-PS to J-PARC-PS. Further unavailable time has to be avoided to keep our activity for detector
R&D. We, in the High Energy Community in Japan, shall make every effort to realize an efficient beam-test
facility at J-PARC.

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