ATF2 proposal. Vol. 2
The two major goals for this facility, called ATF2, are : (A) Achievement of a 37 nm beam size, and (B) control of beam position down to 2 nm level. The scientific justification for the ATF2 project and its technical design have been described in Volume 1 of the ATF2 Proposal. We present here Volume 2 of the ATF2 Proposal, in which we present specifics of the construction plans and the group organization to execute the research programs at ATF2.

title: BEAM DYNAMIC ISSUES IN THE BEPCII LUMINOSITY COMMISSIONING
abstract: As a τ-charm factory like collider, the upgrade project of the Beijing Electron Positron Collider (BEPCII), has reached 1/3 of the design luminosity. During the luminosity commissioning, beam optics recovery, machine parameters measurement, detector solenoid compensation, and instability cure are main problems we met. Besides commissioning the machine, beams were delivered to the users from high energy physics and synchrotron radiation. This paper summarizes the accelerator physics issues in the BEPCII luminosity commissioning from 2009.  BEPCII was designed as a factory-like collider with a design luminosity of 1×10cms at the beam energy of 1.89GeV. It is characterized as “one machine, two purposes”, which means to provide beam not only for high energy physics experiment, but also for synchrotron radiation (SR) users in parasitic or dedicated mode. Using the BEPC tunnel, BEPCII keeps the linac and two transport lines same as BEPC, but was upgraded as two rings in parallel to store e and e beams, respectively, and named as BER and BPR. The two halves of the outer rings are connected as an SR ring, the third ring named as BSR, with 9 beam lines extracted from 5 wigglers, and other 6 beam lines from bending magnets. To save the budget, all the beam line extraction ports are kept the same as BEPC. The layout of BEPCII is shown in Fig. 1.

title: Beam dynamics studies on BEPC- II storage rings at the commissioning stage
abstract: During the 1st and 2nd stages of the commissioning of the upgrade project of the Beijing Electron Positron Collider (BEPC II), which started on Nov. 12, 2006 and Oct. 24, 2007, respectively, we got the luminosity one tenth of its design value, provided beams to synchrotron radiation users for about 4 months, and studied beam dynamics as well. In this paper, some beam dynamics studies on the storage rings and their preliminary results are given.

title: Electron Cloud in Various Kinds of Magnetic Field of BEPCII
abstract: Electron cloud instability (ECI) may take place in a positron storage ring when the machine is operated with a multi-bunch positron beam. According to the actual shape of the vacuum chamber in the BEPCII, a programme which is different from the other simulation codes has been developed. Because of the distance between dipole magnet and sextupole, the quadrupole magnet of BEPCII is very short, much of the photoelectrons can be produced and can move in magnetic fields. The motion of electrons in various kinds of magnetic fields is studied in detail, especially for the solenoid field which will be wound in the vacuum pipe of BEPCII. Simulation shows that the solenoid field is very effective to confine the electrons to the vicinity of the vacuum chamber wall and to make an electron free region at the vacuum pipe Centre.

title: STATUS AND PERFORMANCE OF BEPCII
abstract: BEPCII is the upgrade project of Beijing Electron Positron Collider (BEPC) with its design luminosity of 1×10 cms at the beam energy of 1.89GeV. The construction of BEPCII was completed in May 2008, when the detector worked together with the machine. The collider has been operating for high energy physics since May, 2009, and for synchrotron radiation users since 2007. The status and updated performance of BEPCII are reported here.  BEPCII contains a linac, two transport lines and three storage rings. Among three rings, two are in parallel for e and e beams, respectively, and named as BER and BPR. It locates in the original tunnel of the collider, BEPC, using as many BEPC’s magnets as possible and keeping all the BEPC beam lines extraction ports unchanged. The collider was designed as a factory-like one with a design luminosity of 1×10cms at the beam energy of 1.89GeV. BEPCII is characterized as “one machine, two purposes”, which means to provide beam not only for high energy physics experiment, but also for synchrotron radiation (SR) users in parasitic or dedicated mode. The two halves of the outer rings are connected as an SR ring, the third ring named as BSR, with 9 beam lines extracted from 5 wigglers, and 6 beam lines from bending magnets, as shown in Fig. 1.  Layout of the BEPCII storage rings. The linac finished its construction in 2004 and started commissioning in 2005. After the installation of storage rings for one and a half years, the commissioning of the rings started from Nov. 2006. Later, in 2007, the linac reached all the design parameters. Table 1 lists the main design parameters of BEPCII. In this paper, the linac upgrades are first described. Then the commissioning of the storage rings in last year is reviewed, and finally the operation of BEPCII for the users is given.  Main design parameters of the BEPCII Energy for collision GeV 1.89 Beam current in collision mA 910 Energy for SR GeV 2.5 Beam current in SR mA 250 Injection energy GeV 1.89 – 2.5 Injection rate (e, e) mA/min 50, 200

title: Design studies on the ERL-FEL test facility at IHEP, Beijing
abstract: A proposed compact ERL test facility at THEP, Beijing, is presented in this paper, and includes the design parameters, the essential lattice, and the key components features, such as the photocathode DC gun and the CW superconducting accelerating structures. Some important beam physics issues such as the space charge effect, the coherent synchrotron radiation (CSR) effect and the beam break-up (BBU) effect are briefly described with the simulation results.

title: Next-to-leading order QCD predictions for the signal of dark matter and photon associated production at the LHC
abstract: We study the potential of the LHC to discover the signal of dark matter associated production with a photon induced by a dimension six effective operator, including next-to-leading order QCD corrections. We investigate the main backgrounds from the standard model, i.e. $Z$ boson and a photon associated production with invisible decay of $Z$ boson, and $Z$ boson and a jet production with the jet misidentified as a photon. We find that the ${p}_{T}^{\ensuremath{\gamma}}$ distributions of the backgrounds decrease faster than that of the signal with increasing of the transverse momentum of the photon. The ${\ensuremath{\eta}}^{\ensuremath{\gamma}}$ distributions of the backgrounds are almost flat in the full range of ${\ensuremath{\eta}}^{\ensuremath{\gamma}}$. In contrast, the signal lies mainly in the central region of ${\ensuremath{\eta}}^{\ensuremath{\gamma}}$. These characteristics may help to select the events in experiments. We show that in the parameter space allowed by the relic abundance constraint, which we have calculated at the next-to-leading-order QCD level, the LHC with $\sqrt{S}=7\text{ }\text{ }\mathrm{TeV}$ may discover this signal at the $5\ensuremath{\sigma}$ level after collecting an integrated luminosity of $1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. On the other hand, if this signal is not observed at the LHC, we can set a lower limit on the new physics scale at the $3\ensuremath{\sigma}$ level.

title: Beam instabilities measurement and cures at HLS
abstract: In Hefei light source (HLS), coupled-bunch instabilities are major limiting factors in achieving higher beam intensity while maintaining good beam quality. To Measure and suppress beam instabilities, turn-by-turn (TBT) measurement and bunch-by-bunch(BxB) measurement & feedback system are under commission [1][2]. The design of the two systems and primary experiment results is presented. Measurement and detail analysing results in injection status will also be shown.

title: A closed orbit measurement with the NSRL BPM system
abstract: The beam position monitor system (BPM) of NSRL electron storage ring have a resolution of 10 microns with an accuracy of 50 microns, which is adequate fix beam position measurement and the closed orbit correction. The paper describes both of the BPM system and the closed orbit measurement.

title: The design study of the BTCF lattice

title: Design Issues for the ILC Positron Source
abstract: A positron source for the International Linear Collider (ILC) can be designed using either a multi-GeV electron beam or a multi-MeV photon beam impinging on a metal target. The major design issues are: choice of drive beam and its generation, choice of target material, the target station, positron capture section, target vault and beam transport to the ILC positron damping ring complex. This paper lists the ILC positron source requirements and their implications for the design of the positron source. A conceptual design for the ILC is expected to be finished in the next two years. With emphasis on this timescale, source design issues and possible solutions are discussed.