BINA manual. Hossein Mardanpour,Ahmad Ramazani, KVI The Netherlands. June 12, Introduction 2

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1 BINA manual Hossein Mardanpour,Ahmad Ramazani, KVI The Netherlands June 12, 2006 Contents 1 Introduction 2 2 BINA hardware Forward Wall Energy Scintillators E Scintillators Multi Wire Proportional Chambers (MWPC) Backward Ball Target Target holder Backward Ball Vacuum chamber Data acquisition of BINA Electronics of BINA Forward wall Electronics Backward ball acquisition MWPC acquisition Acquisition setup BINA acquisition software Physics with BINA Three nucleon forces effects in p + d elastic scattering p + d breakup channel References 17 1

2 1 Introduction In the last few years, high-precision measurements of the elastic p + d reaction were carried out at KVI with the aim to study three-nucleon forces (3NF). In the near future, a second generation of 3NF studies will be conducted using the new detector system carrying the name Big Instrument for Nuclear-polarization Analysis (BINA). This detector is particularly suited to study the p + d breakup reaction. BINA is composed of two major parts, as shown in Fig. 1. The forward wall which measures the energy, the position, the polarization of proton and at deuteron scattering angles in the range 10-35, and the backward ball part which covers the rest of the polar angle up to 165. The two parts together, therefore, cover almost the entire kinematic phase space of the break-up reaction. Figure 1: Side view of BINA 2

3 2 BINA hardware 2.1 Forward Wall The forward part of BINA has been designed to detect particles at scattering angles in the range It has three main parts, energy scintillators, E scintillators and MWPC s. Particles hit the MWPC and their coordinate is being detected, after which they pass through the E and E scintillators. The last part is used to detect the energy of the particles. The combination of E, E allows particle identification Energy Scintillators Figure 2: Energy scintillators of BINA, forward wall The forward wall energy part is originally designed to measure the energy of the particles and is also capable of detecting the polarization of the scattered particles. It consists of a curved array of scintillators to measure the energy of the particles excluded by two planes of scintillators (up and down) for the detection of secondary scattered particles (polarized). The curved array consists of 10 horizontal scintillator bars as shown in Fig. 3. Each scintillator has dimension of (9 cm, 12 cm, 2.2 m). The energy scintillators stop protons and deuteron in the energy range of up to 100 MeV and below (20 MeV/cm). Fig. 4 shows the structure of the energy scintillators. Also the details of the design are shown in this picture. Two scintillator bars in the middle of the ring have a hole inside to guide the beam pipe. The scintillator bars in the joint of the ring and wings have trapezoid shape instead of rectangular shape. Two photo multipliers at both sides of the scintillator bars are collecting the scintillation light. Such a setup allows to determine the position of scattered neutrons as well (See thesis of Marcel Volkers). 3

4 Figure 3: Geometry of the energy scintillators Figure 4: Specifications of the energy scintillators E Scintillators A thin segmented scintillation are E is used in combination with the E detectors, to discriminate protons from deuteron. Particles with different AMU leave different amount of energy in the E scintillator bars. By combining this with the signal from energy part, the particle identification becomes possible. Furthermore the vertical array structure of the E bars can be combined with the horizontal array structure of the Energy part to locate the particles in the scattering plane. E detectors are located between MWPC and the energy scintillators. It is composed of 12 vertical scintillator bars which are parallel to each other, as shown in Fig. 5. Each bar is readout by two PMTs located at the bottom and 4

5 top of the scintillator. Figure 5: forward wall, E Scintillators The physical dimensions of the E bars are given in Fig. 6. Scintillators which are located at the position of the beam pipe are disconnected into two independent parts. Figure 6: Details of the designated E bars Multi Wire Proportional Chambers (MWPC) Multi wire chambers are used to detect the coordinate of charged particles in the nuclear physics experiments. The size and precision of the chambers make it possible to cover a wide range of opening angle. Each MWPC consists of 3 planes, X, Y and U. This planes are parallel array of wires to readout the position of incident particle. X planes is made of parallel vertical wires, Y plane horizontal wires and U plane has 45 horizontal angle. Each plane itself consists of two parallel metal plates connected to a high voltage of 3200 V. The wires are 5

6 Figure 7: First Multi wire chamber of BINA located parallel to each other between these two plates. The volume between two plates is filled with an electronegative CF 4 (80%)+isobutane(20%) gas mixture. Particles which pass through the MWPC ionize the gas. Avalanche electrons are collected on the wires. The coordinate can be derived by extrapolating the wire numbers from X and Y planes. The U-plane is used to avoid ambiguities in case more than one particle hits the chamber. Wires are made of tungsten with a sublayer of gold. It is 20 µm in diameter and can stand 100 grn force. In order to refresh the gas, it is flowing inside the chamber. Also circulating the gas inside the chamber helps to clean dirts and dust inside the chamber. BINA has two MWPCs to trace the trajectory of the particles. The first MWPC is located at 29.7 cm from the target position and has active area of 38 cm by 38 cm. It has 118 wires in X,118 in Y and 148 in U plane, laying parallel to each other. An optional second and larger MWPC can be mounted 43.0 cm from the target. 6

7 2.2 Backward Ball Target Two types of targets can be used for experiments with BINA, solid and liquid targets. In general solid targets are hydrocarbons, CH 2 or another organic substances. Solid targets are used as a proton rich target but the reaction is always accompanied by background reactions. On the other hand, solid targets have the advantages of higher density and easy to manipulate than gas or liquid targets. There is a smart solution to this problem and it is liquid target. It is the pure element and since it is liquid it has higher density than a gas. Experiments with liquid target, have in general small background. However the complexity of a liquid target puts large constrains on its operation. Usually a cryogenic system fails to operate if it is not handled carefully. In a liquid target system, the target gas, like hydrogen, is flowing inside the target cell. By decreasing the temperature of the cell with liquid helium the temperature of the target gas drops to few Kelvin. as a consequence the gas become liquid inside the cell. The target cell is a small chamber surrounded by a thin and transparent foil of CH 2. This foil is glued to the cell through a procedure which includes gluing and baking it in the oven and drying it carefully. The left hand side panel in Fig. 7 shows the target position inside the backward ball and right hand side panel shows the target cell. Figure 8: Target cell abd the position of target inside ball Target holder The target holder of BINA is a separate unit which is able to switch between few targets and can carry liquid target as well as solid targets. The solid targets are mounted on the 80 K shielding of the hydrogen cold head. The liquid target is equipped with different components like, heater, gas circulation system, switching system between targets and temperature sensors. The complete system can move vertically via an air pressure mechanism. With this system different target positions can be selected remotely. The target system is installed on top side of the backward ball. 7

8 2.2.3 Backward Ball Figure 9: backward ball (...It needs an introduction Fig. 9) The backward ball of BINA has 149 detectors with two different thicknesses. The thicker(9cm) elements are placed at angles smaller than almost 100 since the particle energes are generally large in this range. The back angle elements are, threfore chosen with smaller thickness(3cm). These detectors cover almost 80% of the scattering solid angle, angles θ = and a complete azimuthal acceptance (Φ) except for the target holder position. Together with the forward wall, BINA covers nearly the complete solid angle, as shown in Fig. 10. Figure 10: Geometry and the forward opening of the backward ball Each detector at the backward ball is composed of a triangular fast scintillator and a slow phoswitch part which has the same cross section and are glued together. The phoswich scintillator is extended with a light guide and connected to a PMT. Fig. 11 shows the sketch of the inner part of the ball and how the 8

9 triangular shaped detectors are glued to each other. Figure 11: Triangular geometry of the scintillators in the backward ball The structure of the ball as a bulk matter, it consists of two types of volumes which have pentagon and hexagon cross sections. The complete ball is made of these two main building blocks but with different sizes and details. In fact it is possible to make a complete sphere with these pentagons and hexagons. Fig. 12 shows how it is possible to make these pentagons and hexagons from triangular building blocks. Figure 12: Pentagons and Hexagones which are the building blocks of Ball Vacuum chamber One of the problems of scattering chambers is their frame and its shadow on detectors. For BINA, this problem does not exit because the detectors of the backward ball form the scattering chamber. The special design of the ball makes it possible to connect vacuum pumps through beam pipe. The vacuum inside 9

10 the ball reaches a pressure of 10 5 mbar, which does not impose a significant energy loss of the particles. At forward angles, the chamber is closed by a this Teflon foil (thickness is 3 mm) glued on a metal frame. The energy loss of particles scattered at forward angles toward the forward wall wall are minimized while preserving the vacuum requirements inside the chamber. Fig. 13 shows its outside sketch. Figure 13: vacuum exit foil 10

11 3 Data acquisition of BINA 3.1 Electronics of BINA Electronics of BINA is divided into three main parts, 1. Forward wall; 2. MWPCs; 3. Backward ball. The forward part collects information which is coming from Energy and E scintillators. At the moment only 20 channels of Energy part are readout plus the complete E part, altogether 44 channels. The backward ball electronics supports all 149 detectors. The MWPC signals are readout using the PCOS III readout system. At the moment every scintillator(not MWPC) in the system can trigger the data acquisition system Forward wall Electronics In this part signals from Energy and E detectors are splitted into two parts. The first part has a direct output which is connected to charge-integrating QDCs (FERA) after a cable delay of 250 ns. The second part is used as input for constant fraction discriminator (CFD). Each CFD module can have 16 input channels and generates individual logic signals used as input for time-to-digitalconverter (TDC) for each channel and a common OR gate. The OR of the FW is used as signal to trigger the DAQ, produce integration gates for the QDCs and a common stop for the TDCs. see Fig. 14. Figure 14: Wall Acquisition scheme Backward ball acquisition Since backward ball has more elements than the other detection parts, its acquisition concerns the major part of the electronics. Signals from 149 detectors are first split into a part which is eventually used as input to the GDCs and a part which is fed into CFDs. The CFD outputs are used for trigger and scaler 11

12 purposes. The QDC signals are split again for a short and long gate integration after a delay of 250 ns. Figure 15: BALL Acquisition scheme MWPC acquisition Multi wire chambers have a dedicated acquisition system in this setup. Each MWPC has three planes, X,Y and U with 169 wires in each plane. So altogether 510 channels are required to support the MWPC. In order to read the data from wires, amplification and discrimination cards are connected to low voltages. The readout system delivers a logical signal, if the signal in the wire passes the threshold. see Fig. 16. X-Plane Y-Plane 118 X-plane 118 Y-plane PCOS II GATE 148 U-plane Figure 16: MWPC Acquisition scheme Acquisition setup After generating a gate from above parts, we make an OR of all gates and generate a global gate. This global gate triggers the acquisition. Fig. 17 shows the main blocks of the acquisition system. The global gate which comes from OR combination of all previous gates from Forward wall and backward ball, generates gate or FERAs, TDCs and PCOS III. In addition, the DAQ is enabled via a logic trigger unit (RCB). In the mean time acquisition produces a busy signal which rejects next events and is released after the DAQ has processed the 12

13 event. The FERAs in the bottom of the picture are responsible for saving the signals of ball and wall. These modules are installed in CAMAC crates which communicate with each other according to Fig. 18. Also each group of FERA modules are driven by a FERA Drv (4301) module (see Fig. 17). When a gate is generated, modules are residual via a DAISAY chain. The data are stored in VMW memory units (DPM). 3.2 BINA acquisition software To explain the acquisition software, we need to separate the programs into three parts. 1. Initialization of electronics. 2. packing the events 3. unpacking the events Electronics initialization software consists of initializing the CFDs of forward wall and the backward ball, FERAs, TDCs, memory units and PCOS modules. The CFD initializer, sets threshold and pulse width and delay time of all CFDs in the acquisition setup. It has GUI to change the numbers for each detector. The rest of the electronics are initialized by DAQ program (stadaq). It checks the status of FERAs consisting of 19 modules for backward ball and 3 modules for forward wall plus three TDC modules. The second item is the event packer. In case the DAQ is triggered, the electronics are readout and the information is packed in an event-by-event scheme. Each event contains the following information, 1. Event number 2. Beam polarization 3. Ball Energy values (150) 4. Ball Energy values (150) 5. Wall Energy value 6. TDC values 7. MWPC channels When the corresponding part does not produce any signal, its part is omitted. Each item has a header word which marks the initial data and tells us how many elements are included. Fig. 19 shows a structure of a sample event. The marked numbers are header words which gives information about the number of channels in the following buffer. To interpret one of the events, we start from first number, which corresponds to the number of data words that are exist in this buffer (Hexadecimal base) 018f(Hex) = 399(Dec). Second number is the event type (always 1, for scaler events it is different). The third number is the beam polarization. Number 3 is the first data from FERAs and it is a header word. The structure of the numbers are given in Fig. 20. Let s interpret one of the buffers. For instance number 20:8002, 8002 (HEX) = 1,0000,000,0000,

14 Figure 17: Overview of the acquisition setup of BINA (bin) is according to the scheme. 20, A header word indicates that 16 data words are following. The virtual station number,vsn, is two which is uniquely defined for each module. The next numbers indicate the QDC data for each channel. For example in this buffer, lets interpret 29:404a. 404a (hex) = 0,1000,0000,1001,010 (bin). Referring to the Fig. 20 reading from right, the first bit is 0 to show that 14

15 Figure 18: Communication between crates it is data word the second 4 numbers is (8 dec) and it represents the channel number the last 11 bits are data value (74 dec). After FERA buffer from first crate, the FERA buffer from second crate (8022, 8023 and 8024) and also TDC buffers (8140, 8141 and 8142) are located. The structure of the buffers from TDC is the same as FERA buffers. the word number 397:ffff, marks the end of the events from FERA and TDC. Buffers after this mark are coming from PCOS. Third item in acquisition software is online/offline analysis program. Basically this program reads events from socket and restores it in an event file. Furthermore it sends a copy of events to the share memory to make it possible to analyze events online. The unpacker program receives a buffer of data words from socket and interprets it, fills it in its trees and restores them for future use. Share memory is part of the memory which is marked by unpacker program and can be accessed by our analysis program. Both packer and unpacker programs are written in C language. They are written such that communication between TCP/IP sockets are possible. The analysis program is a stand alone program which can be fed either from file or from shared memory. It is a ROOT based program and is written in C++ language. //inputbinadataanalysis 15

16 Event 15400: 0:18f, 1:1, 2:0, 3:8001, 4:2f, 5:83e, 6:102f, 7:182b, 8:2020, 9:2834, 10:302b, 11:382a, 12:4026, 13:481c, 14:502f, 15:5823, 16:6028, 17:681d, 18:703c, 19:7835, 20:8002, 21:47, 22:878, 23:103a, 24:1841, 25:2041, 26:2849, 27:3043, 28:383c, 29:404a, 30:4846, 31:504b, 32:5838, 33:604f, 34:6860, 35:7044, 36:7858, 37:8003, 38:32, 39:823, 40:1022, 41:1839, 42:202b, 43:2822, 44:3024, 45:3825, 46:402f, 47:4824, 48:5041, 49:5829, 50:6023, 51:682c, 52:703a, 53:7827, 54:8004, 55:1e, 56:826, 57:1022, 58:1834, 59:2022, 60:2870, 61:302b, 62:382e, 63:402a, 64:4831, 65:5031, 66:5826, 67:6030, 68:6828, 69:702f, 70:7823, 71:8005, 72:16, 73:82f, 74:1020, 75:181d, 76:2031, 77:2835, 78:303d, 79:3829, 80:4032, 81:482c, 82:5032, 83:582b, 84:6053, 85:6838, 86:702e, 87:7854, 88:8006, 89:2c, 90:820, 91:1031, 92:1828, 93:202f, 94:2831, 95:3030, 96:3826, 97:4011, 98:480f, 99:5026, 100:582a, 101:602a, 102:683e, 103:7019, 104:7836, 105:8007, 106:1c, 107:81e, 108:1001, 109:1830, 110:201c, 111:2830, 112:3017, 113:380f, 114:4017, 115:482b, 116:5024, 117:583a, 118:6018, 119:6819, 120:701f, 121:782d, 122:f808, 123:34, 124:826, 125:1028, 126:1820, 127:2028, 128:282a, 129:3046, 130:3810, 131:4027, 132:4824, 133:5024, 134:582a, 135:6819, 136:7028, 137:782c, 138:f809, 139:29, 140:81c, 141:102d, 142:1827, 143:2014, 144:282d, 145:3025, 146:3826, 147:4021, 148:4817, 149:5024, 150:5824, 151:6003, 152:680f, 153:781d, 154:f80a, 155:7a, 156:81a, 157:103c, 158:1839, 159:2044, 160:2821, 161:3056, 162:382f, 163:402c, 164:4833, 165:502c, 166:583f, 167:60a4, 168:6831, 169:7021, 170:800b, 171:3c, 172:839, 173:1034, 174:181e, 175:2036, 176:2835, 177:3020, 178:3841, 179:4003, 180:4837, 181:5040, 182:583a, 183:603d, 184:6821, 185:7037, 186:7846, 187:800c, 188:47, 189:83d, 190:1041, 191:183d, 192:2049, 193:2838, 194:303f, 195:3835, 196:4047, 197:4842, 198:503e, 199:583a, 200:6042, 201:6845, 202:7040, 203:783f, 204:800d, 205:3c, 206:837, 207:1037, 208:1832, 209:203b, 210:2839, 211:303c, 212:3838, 213:403f, 214:4836, 215:503f, 216:583a, 217:6043, 218:6844, 219:7043, 220:7838, 221:800e, 222:36, 223:839, 224:103b, 225:1835, 226:2035, 227:283a, 228:302d, 229:383a, 230:4037, 231:4838, 232:5038, 233:5828, 234:6038, 235:6839, 236:703b, 237:7836, 238:800f, 239:39, 240:83a, 241:103d, 242:1841, 243:2042, 244:2839, 245:302f, 246:3837, 247:4037, 248:483a, 249:502c, 250:5839, 251:603d, 252:6843, 253:7040, 254:7837, 255:8010, 256:2e, 257:82d, 258:1030, 259:182f, 260:2039, 261:2833, 262:3030, 263:382f, 264:4035, 265:482f, 266:5030, 267:582a, 268:6033, 269:6830, 270:7033, 271:782c, 272:8011, 273:2a, 274:828, 275:1026, 276:1822, 277:2033, 278:2824, 279:302d, 280:382a, 281:402e, 282:4827, 283:502d, 284:582a, 285:602b, 286:6830, 287:7026, 288:782b, 289:8012, 290:3b, 291:838, 292:103f, 293:1835, 294:203a, 295:2835, 296:3041, 297:382c, 298:4037, 299:482c, 300:503f, 301:5831, 302:6030, 303:6832, 304:702c, 305:7834, 306:8013, 307:3c, 308:83d, 309:1042, 310:183e, 311:2044, 312:283e, 313:303e, 314:383d, 315:4044, 316:4840, 317:504a, 318:5840, 319:603f, 320:6841, 321:703f, 322:783d, 323:8022, 324:1a, 325:815, 326:1015, 327:1818, 328:2013, 329:2809, 330:3019, 331:3813, 332:4018, 333:4814, 334:501b, 335:5818, 336:601c, 337:6825, 338:7014, 339:780e, 340:8023, 341:1c, 342:814, 343:101a, 344:1818, 345:201c, 346:2819, 347:301c, 348:3814, 349:401b, 350:4817, 351:5019, 352:581c, 353:601e, 354:6818, 355:7012, 356:7813, 357:8024, 358:13, 359:814, 360:1015, 361:1810, 362:2014, 363:2811, 364:3016, 365:380c, 366:401a, 367:480e, 368:5017, 369:580c, 370:6010, 371:6812, 372:7010, 373:7812, 374:8140, 375:5d, 376:95, 377:1a2, 378:206, 379:227, 380:236, 381:2639, 382:2649, 383:26c0, 384:26d1, 385:26e1, 386:26f3, 387:282f, 388:2873, 389:8141, 390:4809, 391:481a, 392:482b, 393:483c, 394:484c, 395:485d, 396:8142, 397:ffff, 398:c400, Figure 19: Information inside an event Figure 20: The structure of the FERA data words 16

17 4 Physics with BINA 4.1 Three nucleon forces effects in p + d elastic scattering 4.2 p + d breakup channel 5 References List of Figures 1 Side view of BINA Energy scintillators of BINA, forward wall Geometry of the energy scintillators Specifications of the energy scintillators forward wall, E Scintillators Details of the designated E bars First Multi wire chamber of BINA Target cell abd the position of target inside ball backward ball Geometry and the forward opening of the backward ball Triangular geometry of the scintillators in the backward ball Pentagons and Hexagones which are the building blocks of Ball 9 13 vacuum exit foil Wall Acquisition scheme BALL Acquisition scheme MWPC Acquisition scheme Overview of the acquisition setup of BINA Communication between crates Information inside an event The structure of the FERA data words