DQBA Lattice Option for the KEK-LS Project
DQBA Lattice Option for the KEK-LS Project
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KEK-LS 项目的 DQBA 晶格选项
DOI：
10.18429/jacow-ipac2017-wepab043
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
A. Ueda
中科院分区：
文献类型：
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作者：
K. Harada;N. Higashi;S. Liuzzo;S. Nagahashi;N. Nakamura;S. Sakanaka;A. Ueda
KEK- ls是第四代3GeV光源，将在KEK筑波校区建造。该晶格由20个ESRF型HMBA（混合型多弯消色差）单元组成，具有短直截面，可使插入设备光束线的数量增加一倍。周长约570m，水平自然发射度约133pmrad。概念设计报告（CDR）于2016年10月发布。在CDR中，在原晶格的短直段添加两个四极磁体，提高了晶格设计的灵活性、发射度和动态孔径。在这个演示中，我们展示了KEK-LS项目的这个新的DQBA（双四倍弯消色差）点阵选项。KEK-LS是将在日本筑波建设的3GeV光源项目。该晶格是为ESRF EBS项目[1]开发的HMBA类型。我们从具有20个单元的3GeV EBS示例晶格开始设计。为了使插入装置[3]的数量增加一倍，增加了1.2 m的短直段。由于原始示例晶格具有非常小的振幅和动量依赖的调谐位移，并且导致较大的动态孔径，因此在晶格研究过程中积累了小的畸变，从而使动态孔径和晶格柔性变差。为了恢复和提高性能，在短直段[4]上增加了两个四极杆。类似的晶格已经在DIAMOND II中作为DTBA[5]进行了测试。在此基础上，我们将改进的HMBA晶格称为DQBA。在本报告中，我们展示了现有CDR版本晶格的不足和DQBA晶格对于KEK-LS的优势。CDR版本晶格的参数见表1，光学器件见图1 (a)。首先，Touscheck ___________________________________________†kentaro.harada@kek.jp (a) (b) (c) CDR残余色散（5m） [cm] 2.5 0.0 0.0（短直）[cm] 2.0 3.0 0.0 RF电压VRF[MV]桶高% 4.5 4.5 4.0能量损失MeV/rev 0.30 0.26 0.26动量压缩α [x10] 2.2 2.4 3.1 Betatron调谐（hor.）νx 48.58（垂直）νy 17.62阻尼时间（小时）[ms] 29.3 21.5 23.4（版本）[ms] 38.3 43.1 43.1（纵）[ms] 22.6 43.4 37.2束流[mA] 500 500 500 Hor发出。(IBS) (pm⋅rad) 133(有效,5秒。)(pm⋅rad) 160(有效,短圣)(pm⋅rad) 225 204 (500 ma withIBS) (pm⋅rad) 315 228 366耦合(500毫安)(%)2.6 3.5 2.2垂直发射率(pm⋅rad) 8.2 8.0 8.1动力孔径(%)2.8 4.0 4.0水平孔(σ)150 200 200 Touschek一生[h] 2.4 17.0 27.0能量分散(0 ma) x10 6.4 7.2 6.7(500毫安)x10 7.9 9.7 8.5群马(0)毫米长度2.7 2.8 2.9(500毫安)毫米3.3 3.8 3.8 47.10 17.15 2.5 DQBA 253 121表1:参数环图1:正常细胞的光学。(c) DQBA的完全消色差(b) DQBA的5m截面消色差(a)当前CDR版本IPAC2017，哥本哈根，丹麦WEPAB043 02光子源和电子加速器A05同步辐射设施ISBN 978-3-95450-182-3 2675版权所有©2017 CC -B Y3。由于动态动量孔径约为3%，因此其寿命约为2小时。在混合模式（最低寿命模式）下，估计的光束损耗大约是目前PF环的三倍。这可能是允许的，但寿命越长越好。其次，由于低水平β和直线段的残余色散，插入装置导致发射度增长[6]。由于长直线段的消色差可以通过15%左右的有效发射度衰减来实现，短直线段的消色差导致发射度非常大。在短直线段，剩余色散为2.5 cm，水平beta函数为0.66 m。在这些参数的作用下，60 cm长度的短真空插入装置的发射度显著增加。DQBA选项DQBA选项最初是与ESRF合作开发的。它具有比CDR版本更好的发射度和孔径。与CDR型晶格相比，将两个四极杆新安装在短直截面上，提高了光学灵活性。对于较短的直线段，水平β函数可以较大以提高I2，色散为零可以抑制I5。图1和0 50 100 150 200 250 300 350 400 -4 -2 0 2 4 Dy na mi c Ap ert ure [Δ X/ σ X]动量（%）(a) CDR
KEK-LS is a fourth generation 3GeV light source and will be constructed in KEK Tsukuba campus. The lattice is 20 cells of ESRF type HMBA (Hybrid Multi Bend Achromat) with short straight section that enables to double the numbers of insertion device beam lines. The circumference is about 570m, and the horizontal natural emittance about 133pmrad. The conceptual design report (CDR) was published in October 2016. Adding two quadrupole magnets to the short straight section of the original lattice in CDR, the lattice design flexibility, emittance and dynamic apertures are improved. In this presentation, we show this new DQBA (Double Quadruple Bend Achromat) lattice option for KEK-LS project. INTRODUCTION KEK-LS is the 3GeV light source project will be constructed in Tsukuba, Japan. The lattice is HMBA type developed for the ESRF EBS project [1]. We start the lattice design from the example lattice of 3GeV EBS with 20 cells [2]. The short straight section of 1.2 m was added in order to double the number of the insertion device[3]. Since the original example lattice has very small amplitude and momentum dependent tune shifts and results in the large dynamic apertures, the small distortions were accumulated during the lattice studies and the dynamic apertures and lattice flexibility become deteriorated. In order to recover and improve the performance, the two quadrupoles are added to the short straight sections [4]. The similar lattice was already examined for the DIAMOND II as DTBA [5]. Following this, we call the improved HMBA lattice as DQBA. In this presentation, we show the shortage of present CDR version lattice and advantage of the DQBA lattice for the KEK-LS. SHORTAGE OF CDR LATTICE The parameters of the CDR version lattice is shown in Table 1 and the optics in Figure 1 (a). Firstly, the Touscheck ___________________________________________ †kentaro.harada@kek.jp (a) (b) (c) CDR Residual dispersion (5m) [cm] 2.5 0.0 0.0 (short straight) [cm] 2.0 3.0 0.0 RF voltage VRF[MV] Bucket height % 4.5 4.5 4.0 Energy loss MeV/rev 0.30 0.26 0.26 Momentum compaction α [x10] 2.2 2.4 3.1 Betatron tune (hor.) νx 48.58 (vertical) νy 17.62 Damping time (hor.) [ms] 29.3 21.5 23.4 (ver.) [ms] 38.3 43.1 43.1 (longitudinal) [ms] 22.6 43.4 37.2 Beam current [mA] 500 500 500 Hor. emit. (no IBS) [pm⋅rad] 133 (effective, 5m sec.) [pm⋅rad] 160 (effective, short st.) [pm⋅rad] 225 204 (500mA withIBS) [pm⋅rad] 315 228 366 Coupling (500mA) [%] 2.6 3.5 2.2 Vertical emittance [pm⋅rad] 8.2 8.0 8.1 Momentum aperture [%] 2.8 4.0 4.0 Horizontal aperture [σ] 150 200 200 Touschek lifetime [h] 2.4 17.0 27.0 Energy spread (0mA) x10 6.4 7.2 6.7 (500mA) x10 7.9 9.7 8.5 Bunch length (0mA) mm 2.7 2.8 2.9 (500mA) mm 3.3 3.8 3.8 47.10 17.15 2.5 DQBA 253 121 Table 1: Parameters of the Ring Figure 1: Optics of the normal cell. (c) Complete achromat for DQBA (b) 5m section achromat for DQBA (a) Present CDR version Proceedings of IPAC2017, Copenhagen, Denmark WEPAB043 02 Photon Sources and Electron Accelerators A05 Synchrotron Radiation Facilities ISBN 978-3-95450-182-3 2675 Co py rig ht © 20 17 CC -B Y3. 0 an d by th er es pe ct iv ea ut ho rs lifetime is about 2 hours because the dynamic momentum aperture is about 3%. For this lifetime, the estimated beam loss is about three times larger than the present PF ring during the hybrid mode (lowest lifetime mode). It may be permissive but longer lifetime is better. For the second, the insertion device cause the emittance growth [6] because of the low horizontal beta and the residual dispersion at the straight section. Since the achromatic long straight section can be realized by about 15% effective emittance deterioration, the achromat of the short straight section results in the very large emittance. At the short straight section, the residual dispersion is 2.5 cm and the horizontal beta function 0.66 m. With these parameters, The short in-vacuum insertion device of 60 cm length results in the significant emittance growth. DQBA OPTION The DQBA option was firstly developed in collaboration with ESRF. It has better emittance and apertures than CDR version. Comparing with CDR version lattice, the two quadrupoles are newly installed to the short straight section and the optics flexibility is improved. For the short straight section, the horizontal beta function can be larger to improve I2, and dispersion zero to suppress I5. Figure 1 and 0 50 100 150 200 250 300 350 400 -4 -2 0 2 4 Dy na mi c Ap ert ure [Δ X/ σ x ] Momentum (%) (a) CDR