Lancaster University, Cockcroft Institute, Security Lancaster Compact Radio Frequency Technology for Applications in Cargo and Global Security Graeme Burt Lancaster University, Cockcroft Institute, Security Lancaster

Smuggling and Global Trade Illicit drug trade worldwide estimated to be $400bn Illicit cigarette smuggling in EU alone €90bn, tax loss of around €16bn Illegal wildlife trade $10-20bn worldwide Counterfeit goods make 7% of world trade. In Europe alone it costs €400bn to legitimate trade

Current Contraband Threats to Europe Arms Smuggling from North Africa via Italy, by some 3600 organised criminal gangs across Europe Cigarettes in large quantities from Russia via Balkan states Drugs from South America via Spain https://euobserver.com/justice/127224

Use of LINAC Based Inspection Systems Revenue generation by collecting duties and taxes (Biggest benefit) Protection from drug smuggling in large quantities (Second biggest benefit) Deterrent to weapons and explosive smuggling

Examples of Effectiveness UK Government deployed 10 scanners initially and within 2 years time, cross-channel cigarette smuggling fell by 70%, cutting it by 5 billion sticks per year and protecting £6 billion per year revenue In Virginia USA 732 pounds of cocaine was seized in a cargo shipment of orange juice cans, street value of $644 Million(Dec 2013) In May 2014, Spanish authorities found 2.5 metric tons of narcotic hidden in a shipment of pineapples At Rotterdam port in Dec 2014, 3.5 Tons of cocaine was caught hidden in a shipment of cassava roots originated in Costa Rica http://www.ticotimes.net/2014/12/30/drug-scanners-sit-unused-as-drugs-pass-through-limon-port From I. Tahir, Rapiscan, APAE meeting

Cargo Screening Accelerators Aircraft ULD or pallets are too large for baggage scanners and too small for cargo scanners. Currently searched by hand. Luggage Scanning requires a few tens to hundreds keV. This can be delivered by traditional X-ray tubes up to 450 keV. Ideal energy is around 1-2 MeV but no current source available. Truck or shipping cargo is larger requires ~6 MeV. Industrial linacs can provide this.

X-Band RF Applications Low Energy, Low Output: 1 MeV, up to 2 cGy/min at 1m @ 100 Hz. Air cargo screening  inspect a full ULD: No system currently exists to achieve the required penetration and spatial resolution, A 1 or 2 MeV based LINAC inspection system has the potential to open up this new market sector. Mobile screening with a small exclusion zone: Current mobile screening systems require 40m x 40m exclusion zone  protect public. A low energy and dose rate LINAC can: significantly reduce the exclusion zone footprint, allow scanning in public areas i.e. sporting events, car parks, concerts, etc.

Why X-band? (2rcavtshield + tshield2)p For a mobile linac mounted on a robotic arm the weight of the linac is critical. While the linac isn’t very big or heavy the shielding is. X-band means that the shielding diameter is much less. Area of shielding is given by (2rcavtshield + tshield2)p Availability of 9.3 GHz magnetrons

Cargo Screening Accelerators X-band technology chosen due to: availability of technology compactness technological limits to robustness tolerances at high power in micromachining and brazing. Existing Linac suppliers: Varian (USA) – 65% market Siemens (USA) Nutech (China) Linear Accelerators account for 90% of the sources used in high energy cargo screening. It is expected that the global market is ~few hundred units/year. In 2007, 250 units were sold internationally. Data provided by Rapiscan Global Sales and Marketing (2007)

CLASP Ph-I Collaboration Team Rapiscan Systems: Ed Morton (Rapiscan PI) Imran Tahir (Magnetron Controls) E2v: Stuart Andrews (Gun/Magnetron) Cliff Weatherup (e2v PI) Tushar Ghosh (Gun) Trevor Cross (e2v PI) Lancaster University: Graeme Burt (Project Leader) Praveen Ambattu (Linac) Chris Lingwood (Linac) Tom Abram (Mechanical) Mike Jenkins (Linac) – Now at ASTeC STFC, ASTeC Daresbury Lab: Ian Burrows (Mechanical Eng.) Peter Corlett (Project Manager) Andrew Goulden (Cooling Sys.) Paul Hindley (Installation) Peter McIntosh (ASTeC PI) Keith Middleman (Vacuum) Rob Smith (Beam Diagnostics) Chris White (Electrical Eng.) Steve Griffith (electrical) Travor Harnett (Electrical)

CLASP 1 MeV System (Funded Phase-I) DC Electron Gun e2V collaboration X-ray Target Rapiscan collaboration Buncher and Accelerating Structure (1 MeV) CI Proposal Scope Phase-I Magnetron e2V collaboration (8-12 GHz, 1-2 MW, 100-200 Hz) Dynamic switching of amplitude and phase pulse-to-pulse) Automated Control System (Energy, rep-rate, dose) Proprietary Rapiscan Imaging and Data Analysis

Stability against frequency detuning and losses From the single chain model of ‘N+1’ coupled cavities, the eigenfunction for mode ‘m’ and cell ‘n’, can be written as, k Now incorporating frequency shift and losses to the cells, then the modified eigenfunction is given by, Amplitude fluctuation can be caused by frequency errors caused from fabrication errors Phase error can be caused by the cavity losses (wall and beam loading) Mode Amplitude error Phase error zero Δf/f 1/Q p/2 (Δf/f)2 Nil p 1) T. Wangler, RF Linear accelerators, 2) E.A. Knapp, SW high energy linac structures, Rev. Sci. Instr. 1968

Bi-periodic cavity p/2 modes are more stable than p modes as the contribution from the modes above and below cancel and they have a large separation to the next nearest mode high shunt impedance p-mode high field stability p/2-mode p/2-mode bi-periodic L both ! L a p Coupling cavity Accelerating cavity Beam sees a p-mode high acceleration RF sees a p/2-mode field highly stable

RF bunching and focusing Solenoids are unacceptable for compact applications. Hence RF focusing from the linac structure is used Radial focusing (long. Debunching) Initially the DC bunch see’s all phases, bunching phases are captured The captured bunch then is accelerated moving towards the peak acceleration The bunch is then moved to a radially focussing phase until the linac exit which unfortunately starts to debunch the beam. CI-SAC Nov 2010

1 MeV Buncher/Accelerator 17 keV

1 MeV Linac Design 5 mm beampipe diameter 3.5 mm iris thickness Parameter Value Energy 1 MeV Frequency 9.3 GHz Length 130 mm Rsh max 116 M/m Pin 433 kW Pulse Length 4 s Pulse Rate 250 Hz Peak Beam Current 70 mA Average Beam Power 70 W 5 mm beampipe diameter 3.5 mm iris thickness 1 mm coupling cell thickness Gradient (MV/m) E (MeV) Ibeam (mA) Spot Size (mm) 20 (nom) 1.08 70 1.6 +10 % +11 % -4 % +58 % -10% -27 % -33 % -55 % Voltage (kV) E (MeV) Ibeam (mA) Spot Size (mm) 17 (nom) 1.08 70 1.6 +10 % +0.8 % -3.5 % +48 % -10% -7 % -20 % -15 %

Beam Tracking Analysis Particle Tracking initially performed in ASTRA. Collaboration with Tech-X UK to verify Linac electron beam capture and tracking. Using VORPAL code to validate PIC transport. Good comparison was found between both methods. http://www.txcorp.com/products/VORPAL/

Launch radius=0, Momentum vs Z 2.09 MeV 1.58 MeV 1.19 MeV 0.59 MeV Here ‘phi’ is the particle launch phase with respect to the phase giving maximum energy

Linac Fabrication Fabrication commissioned with UK industry: Shakespeare Engineering, Ltd Geometric tolerances of 10 m required. Diamond machining and vacuum brazing processes employed. http://www.shakespeareengineering.co.uk/

Cavity Tuning Structure was found to have poor matching and field flatness

Lancaster/STFC X-band structure We have developed a new X-band structure with much greater cell-to-cell coupling to increase tolerances. Simple structure design with no slots to help tolerances (low fields and low voltage make this acceptable) Built by Comeb, Italy

Diagnostics Line In order to fully diagnose the beam from the linac we have a diagnostics line fitted to the output. We have a motorised section which can either provide a slit, a screen, a tungsten target or vacuum.

Beam properties Spot size measured on phosphor screen at 3 mm. This is a few cm away from the linac so we still need to work out the size at the linac exit. We capture around 30-40% of the current emitted from the gun.

3-4.5 MeV S-band linac Higher energy reach. Simpler to manufacture. Pi mode structure.

From J. O’Malley AWE, APAE meeting

Higher Energy LINACs As Gamma-Ray Source Recent theoretical/experimental work shows that a gamma beam from LINACs with energies higher than 10.6MeV can excite stable nitrogen isotope in explosive (N14) to radioactive isotope (N13), emitting positrons. The positron produces two 0.5MeV photons that are easily detectable Same technique can be used to detect land mines as well using 17MeV LINAC As Photo-neutron Source Intense photo-neutron beam can be a reliable way of detecting explosives and nuclear materials LINACs with energy levels above 8Mev and with converter materials such as Be and D2O in the X-Ray beam path can produce intense photo-neutron beams http://isif.org/fusion/proceedings/fusion01CD/fusion/searchengine/pdf/ThA27.pdf http://connection.ebscohost.com/c/articles/61237783/intense-photoneutron-sources-nuclear-material-detection http://www.researchgate.net/publication/232386840_Explosives_detection_using_photoneutrons_produced_by_X-rays From I. Tahir, Rapiscan, APAE meeting

Potential Linac solution Could a high gradient linac offer 17 MeV electrons in 35 cm? Its 50 MV/m which is certainly less than achieved using CLIC technology, but impedance is the issue. There would not be space for an XL-5 or several smaller tubes. Lets limit to a 7 MW with a PC. Using a structure almost identical to an undamped CLIC structure would meet the requirements for this application. Changing the beam current will allow the voltage to be adjusted.

Other Current/Future developments Time of flight Compton Backscatter Alloys 3D images to be created with access to only one side. Handling distortion cased by intensity dropping with distance is a challenge. Improved resolution can be achieved with smaller pulse lengths with higher current. Needs a higher current due to low backscattered dose. CW linacs Lower peak dose, and easier for detector to deal with temporally. Phase contrast Offers better contrast for low Z materials (a weakness in X-ray scanners).

Conclusion Through PNPAS, a strong UK collaborative team has been formulated to successfully demonstrate a working system solution. A new S-band linac has been developed Future applications will need higher repetition rate and/or higher energies A CLIC/VHEE like structure with a 7 MW klystron and a PC could meet the high gradient requirements.