The Alignment of DTL in CSNS Institute of High Energy Physics, CAS KE Zhiyong

Page 散裂中子源进展汇报 July 14, Outline 1.General Layout of CSNS 2.General Introduction of DTL 3.Alignment Tolerance Requirement of DTL 4.Procedure of DTL Alignment 5.Analysis on the Final Position Error of DTL

Page 散裂中子源进展汇报 July 14, General Layout of CSNS CSNS mainly consists of an H - linac and a proton rapid cycling synchrotron(RCS). It is designed to accelerate proton beam pulses to 1.6 GeV kinetic energy at 25 Hz repetition rate, striking a solid metal target to produce spallation neutrons.

Page 散裂中子源进展汇报 July 14, General Introduction of DTL The DTL(Drift Tube Linac) is part of the Linac accelerator which accelerates H - ion from 3 MeV to 80 MeV. It consists of four independent DTL tanks, and each DTL tank is made up of three DT mechanical sections. A total of 153 drift tubes will be installed precisely in the DTL tank. DTL mechanical sectionDifferent kinds of drift tubes

Page 散裂中子源进展汇报 July 14, Alignment Tolerance Requirement of DTL RMS ΔX (mm) Transverse offset ΔY (mm) Vertical offset ΔZ (mm) Longitudinal offset DTL in the Linac The alignment accuracy of DTL is 0.05mm both in the transverse and vertical direction, and 0.10mm in the longitudinal direction.

Page 散裂中子源进展汇报 July 14, Procedure of DTL Alignment The alignment of DTL is a complicated work which consists of five steps as below. 1. DT mechanical section fiducialization2. Drift tubes fiducialization 3. Drift tube installation 4. Drift tube adjustment 5. DT mechanical section installation

Page 散裂中子源进展汇报 July 14, DT mechanical section fiducialization The DT mechanical section fiducialization is to establish a coordinate system on the DT mechanical section which provides the reference to install and position the drift tubes. Coordinate system of the DT mechanical section: Origin: projected point of internal circle center on low- energy end surface Z axis: connecting line from origin to projected point of internal circle center on high- energy end surface Y axis: line perpendicular to the top plane Handedness : right

Page 散裂中子源进展汇报 July 14, it will take about 4 hours to fiducialize the DT mechanical section, and the fiducialization accuracy is about 0.02mm. Both on the low-energy end and high-energy end are fixed five reflector seats and they are the control points when installing and adjusting the drift tubes. The alignment work is carried on in the laboratory which is kept at a constant temperature and humidity as the same condition in the lilac tunnel.

Page 散裂中子源进展汇报 July 14, Coordinate system of drift tube: Origin: projected point of excircle center on low-energy end surface Z axis: connecting line from origin to excircle center Y axis: line perpendicular to the top plane of drift tube Handedness : right 4.2 Drift tube fiducialization The drift tube fiducialization is to establish a coordinate system on the drift tube which provides the reference when the drift tube be installed and positioned in the DT mechanical section.

Page 散裂中子源进展汇报 July 14, The machining accuracy of all kinds of reference pieces which are specially designed is 0.01mm. Different kinds of reference pieces There are nine types of drift tube pallets correspond to the drifts tubes.

Page 散裂中子源进展汇报 July 14, Laser tracker Support base Straight edge inch laser reflector Internal hole reference base Drift tube inch reflector seat Pallet-tangent plate Excircle reference base 1.5 inch laser reflector Straight edge reference base Marble platform The drift tube fiducialation is carried out on marble platform, and the drift tube is placed in the designed pallet. Laser tracker is used to find out the coordinate of the four inch reflector seats (reflector attached) in the coordinate system established on drift tube. Drift tube pallet Fiducialation facility

Page 散裂中子源进展汇报 July 14, Before the fiducialization, the appropriate pallet should be on the marble platform and the four inch reflector seats attached in the reserved holes on drift tube with melt adhesive. The drift tube should be adjusted manually to the cylinder axis be perpendicular to the marble platform by using dial gauge.

Page 散裂中子源进展汇报 July 14, The fiducialization accuracy is about 0.015mm. Each drift tube will be fiducialized at least two times, and it will take about 3 hours.

Page 散裂中子源进展汇报 July 14, Drift tube installation The drift tube will be placed in the support mechanism which can slid along the guide rail by pulling the rope slowly. When the drift tube reaches the designated position, pull the rope fixed on the handle of drift tube carefully until the handle passes through the hole on the DT mechanical section and then fix and lock the handle by screws.

Page 散裂中子源进展汇报 July 14, Drift tube adjustment The theoretical X-coordinate and Y-coordinate of the drift tube in the coordinate system of DT mechanical section are equal to the value in the coordinate system of drift tube in the fiducialization, and the Z- coordinate should plus a theoretical distance value. The drift tube should be adjusted to its theoretical position in DT mechanical section, and the cylinder axis of drift tube should coincide with the cylinder axis of DT mechanical section.

Page 散裂中子源进展汇报 July 14, The drift tube is adjusted by the adjusting mechanism fixed on the top plane of DT mechanical section, and laser tracker is used to monitor the position error of drift tube during the adjustment progress. The drift tube adjustment is a hard work which will take about 4 to 8 hours, and the accuracy is about 0.03mm.

Page 散裂中子源进展汇报 July 14, DT mechanical section installation Three DT mechanical sections will be combined into a DTL tank and be installed in the linac tunnel. The accuracy of the DT mechanical section installation is expected to be 0.04mm in the transverse and vertical direction, 0.10mm in the longitudinal direction.

Page 散裂中子源进展汇报 July 14, Analysis on the Final Position Error of DTL DTL Drift Tube Fiducialization Error (mm) DT Section Fiducialization Error (mm) Best-fit Error(mm) Drift Tube Installation Error (mm) DT Section Installation Error (mm) Final Position Error (mm) Tolerance Requirement (mm) ΔX (Transverse offset RMS) ΔY (Vertical offset RMS) ΔZ (Longitudinal offset RMS) The final position error is the geometric sum of five kinds of error and it is very close to the tolerance requirement.

Page 散裂中子源进展汇报 July 14, Normally, It will take 8 ~ 12 hours to fiducialize and install a drift tube into the DT mechanical section, and most of the time is spent on the drift tube adjustment. And it will take about 8 ~10 months to finish the alignment work of 153 drift tubes. It need quite a lot of patience and carefulness to carry out the alignment of DTL to prevent the damage of both the drift tubes and DT mechanical section, which have no spare part.

Page 散裂中子源进展汇报 July 14, Advanced research on alignment of DTL

Page 散裂中子源进展汇报 July 14, The end, thanks!