High Ablation Rates Research Articles

Femtosecond-Laser-Induced Nanostructure and High Ablation Rate Observed on Nitrided Alloy Steel

Femtosecond (fs)-laser-induced nanostructuring of mainly nitrided die steel (1.5C-12Cr) was experimentally investigated using die steel that was heat-treated and then plasma nitrided. Nitrided stainless steel (18Cr-8Ni) and low-carbon steel (0.1C) were also used to examine the influence of the alloy composition. Periodic nanostructures were formed in the direction perpendicular to the laser polarization and the mean spacing D increased with the fluence F. The minimum D values for alloy steels containing Cr observed at F around the ablation threshold were 250–285 nm, which corresponds to a size of about λ/3. In contrast, the minimum D for low-carbon steel was larger at 20 to 30% more than those of the alloy steels. In addition, the ablation rate was obtained by analysis of the cross-sectional profiles of craters ablated by superimposed fs-laser pulses. Although the ablation rates for the non-nitrided steels increased linearly with F on a logarithmic scale, it should be noted that the ablation rate for nitrided die or stainless steels increased faster than linearly with F.

High Precision Laser Processing of Steel Surfaces with Sub-ns-lasers

Ultrashort pulsed lasers like ps- and fs-lasers with single pulses and pulse bursts allow a high ablation rate combined with a superior quality for several materials like copper and brass as well as glass and dielectrics.In case of steel surfaces this known quality could not be transferred, because after a defined ablation depth the surface roughness increases. An increased roughness is mainly caused by a growing area of cone like protrusion structures (CLP) with increasing of the ablation depth. To avoid this phenomenon a melt concomitant ablation, due to some 100ps pulse duration was applied with a moderate pulse energy of 30 μJ. The results show no CLP structures and a decreased surface roughness in combination with an acceptable recrystallization of melt residues around the ablation area. The non-melt-free ablation process with residual molten volume caused by the longer pulse duration (compared to USP-lasers) has to be compensated through a higher laser power. This investigation shows an approach with a parallelization of several separate modulated laser spots for increasing the processing speed.

Evaluation of hepatocellular carcinoma ablation using image fusion assisted contrast-enhanced ultrasound

Objective To evaluate the clinical value of intraoperative image fusion assisted contrastenhanced ultrasound (CEUS) in real-time assessing the curative effect on radiofrequency ablation of hepatocellular carcinoma(HCC).Methods From November 2010 to August 2011,the patients with HCC which would accept radiofrequency ablation (RFA) in our hospital were divided into image fusion assisted CEUS group and conventional CEUS group.The HCC lesion in each group was named as difficult lesion if it was invisible in B-mode ultrasound,larger than 50 mm in diameter or the puncuture route was affected by lung,ribs or blood vessels.Ten minutes after RFA,two groups of patients were performed intraoperative image fusion assisted CEUS examination and conventional CEUS examination respectively.All the patients received CT/MRI one month after ablation to decide whether the HCC had been completely ablated.Difference of complete ablation rate of HCC was compared between the two groups as well as between the difficult lesions in each group.Results Forty-eight lesions in 39 patients were enrolled in image fusion assisted CEUS group including 19 difficult lesions.Sixty-eight lesions in 53 patients were enrolled in conventional CEUS group including 18 difficult lesions.No statistical difference was found between the two groups in lesion size,proportion of difficult lesions,proportion of lesions received TACE or RFA plus PEIT (P =0.052,P =0.136,P =0.185,P =1.000).Postoperation following-up results demonstrated that complete ablation rate of HCC in navigation assisted CEUS group(100 ％,48/48) was not statistically higher than that in conventional CEUS group(92.6％,63/68) (P =0.145).But the difficult lesions in navigation assisted CEUS group (100％,19/19) had statistically higher complete ablation rate than that in conventional CEUS group(72.2％,13/18) (P =0.020).Conclusions Intraoperative navigation assisted CEUS could real-time assess the curative effect on RFA of HCC,especially in the difficult lesions,and could be used as the beneficial supplement of the conventional CEUS. Key words: Ultrasonography; Microbubbles ; Liver neoplasms; Catheter ablation

Influence of the pulse frequency and water cooling on the femtosecond laser ablation of bovine cortical bone

Ultrafast lasers are extremely promising tools for minimally-invasive orthopedic surgery, but the ablated volumes per pulse are low, so a high pulse frequency is necessary to reach practical ablation rates. The purpose of this work was to study in vitro the influence of the pulse repetition rate on the ablation rate, surface topography and surface composition of bone using of bovine cortical femur as a model. The tests were carried out by scanning the laser beam in relation to the sample, using pulse frequencies between 50 and 3000Hz, scanning velocities from 0.5 to 10mm/s and average pulse energy of 650μJ. The experiments were performed in dry conditions and with water irrigation. The higher ablation rates were obtained at high scanning velocity without water irrigation but severe thermal effects such as resolidification, cracking and, eventually, carbonization occurred in these conditions due to heat accumulation in the tissue. Thermal damage was avoided for all the laser processing parameters ranges tested by using water cooling. The highest ablation rate achieved was 1.4mm3/min for a scanning velocity of 10mm/s at 2kHz pulse repetition rate under water irrigation.

Ultrashort pulsed laser (USPL) application in dentistry: basic investigations of ablation rates and thresholds on oral hard tissue and restorative materials

Modern ultrashort pulse lasers with scanning systems provide a huge set of parameters affecting the suitability for dental applications. The present study investigates thresholds and ablation rates of oral hard tissues and restorative materials with a view towards a clinical application system. The functional system consists of a 10 W Nd:YVO4 laser emitting pulses with a duration of 8 ps at 1,064 nm. Measurements were performed on dentin, enamel, ceramic, composite, and mammoth ivory at a repetition rate of 500 kHz. By employing a scanning system, square-shaped cavities with an edge length of 1 mm were created. Ablation threshold and rate measurements were assessed by variation of the applied fluence. Examinations were carried out employing a scanning electron microscope and optical profilometer. Irradiation time was recorded by the scanner software in order to calculate the overall ablated volume per time. First high power ablation rate measurements were performed employing a laser source with up to 50 W. Threshold values in the range of 0.45 J/cm(2) (composite) to 1.54 J/cm(2) (enamel) were observed. Differences between any two materials are statistically significant (p < 0.05). Preparation speeds up to 37.53 mm(3)/min (composite) were achieved with the 10 W laser source and differed statistically significant for any two materials (p < 0.05) with the exception of dentin and mammoth ivory (p > 0.05). By employing the 50 W laser source, increased rates up to ∼50 mm(3)/min for dentin were obtained. The results indicate that modern USPL systems provide sufficient ablation rates to be seen as a promising technology for dental applications.

Microstructuring Tools for Sheet Bulk Metal Forming - A Designated Application for Picosecond

In addition to coatings, microstructures can increase abrasion-resisting quality of sheet bulk metal forming tools by influencing friction conditions. The use of ultrashort pulsed lasers offers a possibility for manufacturing flexible microstructures with very high precision. Thus the processing with picosecond laser allows the generation of structures with dimensions down to the range of single microns. Because of the characteristic ablation process temperature sensitive materials can be structured without any heat transfer into the material. Applying appropriate processing parameters avoids complex post-finishing processes because of the achieved good structure qualities without any melt and any material throw-up. For implemention of a fast structuring process with high ablation rates it is shown, that only fluences near the ablation threshold allow a processing result of high quality and with the maximum ablation efficiency.

The search for seismic signatures of movement at the glacier bed in a polythermal valley glacier

AbstractA passive seismology experiment was conducted across the main overdeepening of Storglaciären in the Tarfala valley, northern Sweden, to investigate the spatial and temporal distribution of basal microseismic waveforms in relation to known dynamics of this small polythermal sub-arctic glacier. The high ablation rate made it difficult to keep geophones buried and well coupled to the glacier during the experiment and reduced the number of days of good-quality data collection. The characterization of typical and atypical waveforms showed that the dominant waveforms were from near-surface events such as crevassing. Waveforms resembling basal microseismic signals were very rare, and seldom observed on more than two seismic stations simultaneously. The analysis of waveforms, amplitudes and particle motions suggested a near-field origin for most events. Even though basal sliding is known to occur in the overdeepening, no convincing examples of basal waveforms were detected, suggesting basal microseismic signals are rare or difficult to detect beneath polythermal glaciers like Storglaciären. We discuss the reasons for failing to locate basal signals, consider the origin of common waveforms and make recommendations for setting up passive seismology experiments on glaciers with high ablation rates.

Thyroid hormone replacement one day before (131)I therapy in patients with well-differentiated thyroid cancer.

Objective:The current study aimed to determine the efficacy of radioiodine-131 (131I) ablation therapy with thyroid hormone replacement one day before 131I administration in patients with well-differentiated thyroid cancer (DTC).Methods:This retrospective study included 29 patients who underwent 131I therapies twice for DTC during 6-12 months. Since all the patients obviously had residual lesions by their serum thyroglobulin levels or their scintigrams at the first therapies, they underwent the second 131I therapies without diagnostic scintigraphy after the first therapies. After confirming the sufficient elevation of TSH concentration, thyroid hormone replacement was resumed one day before 131I administration (3.7-7.4GBq). The ablation rate of thyroid remnant at the first 131I therapy was evaluated by comparing 131I post-therapeutic images of the two treatments.Results:Three patients were administrated thyroid hormone after 131I therapy because of insufficient TSH concentration under thyroid hormone withdrawal. In the remaining 26 patients, 41 thyroid remnant accumulations were detected in all 26 patients at the first 131I therapy. Based on the second 131I post-therapeutic images, successful ablation was confirmed in 24 of 26 patients (92.3%) and 38 of 41 sites (92.7%), which was comparable with historically reported ablation rates.Conclusion:Thyroid hormone replacement one day before 131I therapy could provide a sufficiently high ablation rate in patients with DTC.

Adjuvant thyroid remnant ablation in patients with differentiated thyroid carcinoma confined to the thyroid: a comparison of ablation success with different activities of radioiodine (I-131)

To assess efficiency of various I-131 activities on thyroid remnant ablation in thyroid cancer patients. The significance of patients' characteristics, pathologic features and levels of Tg were analyzed. This study included 259 consecutive differentiated thyroid cancer patients, with disease confined to the thyroid, treated with I-131 after total thyroidectomy. Patients were divided into the three groups: 80 patients receiving low [1110-1850 MBq (30-50 mCi)], 121 intermediate [2775 MBq (75 mCi)] and 58 high [3700 MBq (100 mCi)] postoperative I-131 activities. Six to eight months after the application of radioiodine, measurements of TSH, Tg, anti-Tg antibodies (in hypothyroid state) together with ultrasound exam and whole-body scintigraphy were performed. The ablation was significantly more effective (after the first application) in patients receiving 100 mCi of I-131-89.7% than in patients receiving lower activities (P = 0.016). There was no significant difference in ablation rate between the 30-50 mCi (77.5%) and 75 mCi (70.2%) groups. In the group receiving 30-50 mCi, patients with solitary tumors had significantly higher ablation rate (P = 0.038). In patients receiving 75 mCi ablation rates were higher among older patients (P = 0.005), with infiltration of the single lobe (P = 0.005), and with solitary tumor (P = 0.012). The rates of successful ablation after the second application of I-131 (after 12-16 months) amounted to 96, 97 and 96% in the 30-50, 75 and 100 mCi groups, respectively. The activity of I-131 and age were independent factors for thyroid ablation failure after the first application of I-131 (model of binary logistic regression). The results of remnant ablation were satisfactory with all activities applied. Although after the first application of I-131 the activity of 100 mCi is significantly more effective in thyroid ablation than the administration of 30-50 mCi and 75 mCi, the ablation rates between all the three groups are similar (almost equal) after the second application. Thus, the activity to be administered may depend on patients' characteristics and a detailed consideration of the merits and demerits of each I-131 activity.

Ablation behaviour of a TaC coating on SiC coated C/C composites at different temperatures

To improve the ablation resistance of carbon/carbon (C/C) composites, a TaC coating was prepared by supersonic plasma spraying on SiC coated C/C composites. The microstructure and morphology of the coatings were characterised by Scanning Electron Microscopy and X-ray diffraction. The ablation properties were studied at different temperatures under oxyacetylene torch. At 2100°C, the oxides were blown away and resulted in high ablation rates: 1.2×10−2mm/s and 3.9×10−3g/s. However, most oxides can remain in ablation centre and serve as a coating at low temperature (1900 and 1800°C). Therefore, the TaC/SiC coated samples exhibited zero linear ablation rate and lower mass ablation rate.

Percutaneous microwave ablation for liver cancer adjacent to the diaphragm

Purpose: The aim of the study was to prospectively evaluate the safety and effectiveness of percutaneous microwave (MW) ablation for liver cancer adjacent to the diaphragm.Materials and methods: From May 2005 to June 2008, 89 patients with 96 hepatic lesions adjacent to the diaphragm (the shortest distance from the lesion margin to the diaphragm less than 5 mm), who underwent ultrasound (US)-guided percutaneous MW ablation, were included in the study group. A total of 100 patients with 127 hepatic lesions not adjacent to the diaphragm (the shortest distance from the lesion to the diaphragm and the first or second branch of the hepatic vessels more than 10 mm), who underwent US-guided percutaneous MW ablation, were included in the control group. During the ablation the temperature of marginal ablation tissue proximal to the diaphragm was monitored and controlled at 50°–60°C for more than 10 min in the study group. We compared the results of ablation between the two groups.Results: A total of 91 of 96 tumours (94.8%) in the study group and 123 of 127 tumours (96.9%) in the control group achieved complete ablation (P > 0.05). Local tumour progression was found in 18 of 96 tumours (18.8%) in the study group and 21 of 127 tumours (16.5%) in the control group during follow-up after MW ablation (P > 0.05). No major complications occurred in either group.Conclusions: Under strict temperature monitoring, percutaneous MW ablation is safe and can achieve a high complete ablation rate for the treatment of hepatic tumours adjacent to the diaphragm.

Glacial lake distribution in the Mount Everest region: Uncertainty of measurement and conditions of formation

This study provides a complete mapping (October 2008) of glacial lakes and debris-covered glaciers in the Mount Everest region. These types of analyses are essential in studies of the impact of recent climate change, and therefore the uncertainty of measurements is discussed with the aim of creating a reference study for use when glaciers and lakes are delineated using remote sensing imagery. Moreover, attention is focused on conditions related to the formation of lakes, which is the greatest evidence of the impact of climate change at high altitudes characterized by debris-covered glaciers. Regarding the formation process of supraglacial lakes, our findings confirm that the slope of the glacier where lakes are located is primarily responsible for the low flow velocity of this zone. Otherwise, this study is novel in its identification of a further boundary condition. The slope of the glacier upstream is able to influence both the low flow velocity and the high ablation rates at the glacier terminus. In fact, the imbalance between the two glacier zones generates the down-slope passage of debris, snow and ice. We found the slope of the glacier upstream to be inversely correlated with the relevant total surface of the lakes downstream. The multiple regression model developed in this study, considering the slopes of the two glacier areas distinctly, has been able to predict 90% of the supraglacial lake surfaces. Concerning the surfaces of lakes not directly connected with glaciers (unconnected glacial lakes), we found they are correlated with the dimensions of their drainage basin, whereas no correlation was found with the glacier cover in the basin. Considering that the evaporation/precipitation ratio at these altitudes is approximately 0.34, the evolution of these lakes appears to be a helpful sign for detecting the precipitation trend of these high-altitude regions.

Over-ablation and deflection of hydrogen pellets injected into neutral beam injection heated plasmas in the Large Helical Device

During hydrogen pellet injection experiments in the Large Helical Device (LHD), over-ablation caused by fast ions (due to tangential neutral beam injection (NBI) heating at 150–180 keV beam energy) is shown to dominate the measured penetration depths. The neutral gas and plasma shielding model, including the interaction of the pellet with fast ions, is applied, and its predictions are shown to agree well with the measured Hα emission profiles. The toroidal deflection of the pellet trajectories observed in the direction of beam injection is reproduced by the model when unbalanced ablation on the two sides of the pellet is included. The attenuation of the fast-ion and electron heat fluxes entering the ablation cloud is examined, showing that the high-energy part of the fast-ion distribution function is responsible for the high ablation rates, and that the thermal electron population is not the dominant ablating species. An analytical scaling for the balanced NBI condition is derived, which reasonably reproduces the measured penetration depths included in the LHD database. In the LHD, for given pellet parameters and beam energy, the fast-ion density is shown to be the major parameter affecting the experimental penetration.

Valency control in MoO3−δ nanoparticles generated by pulsed laser liquid solid interaction

The possibility of synthesizing binary oxides nanoparticles in a nano-scaled form by laser liquid solid interaction using a NdYAG “1.064 μm” as an irradiating laser source is reported. The case of MoO3−δ is emphasized. Furthermore, it is demonstrated that the Mo–O electronic valence can be controlled through the coupling effects of oxygen enriched nature of the used coating liquid layer, namely pure H2O or H2O2 and the laser beam fluence. Dark blue hydrated molybdic pentoxide Mo2O5·xH2O and yellow molybdenum trioxide MoO3 nano-suspensions were reproducibly synthesized with hydrogen peroxide and water, respectively, at a relatively high ablation rate. The average size of the molybdenum trioxide nanoparticles was about ~8 nm, slightly larger than the molybdic pentoxide ones “ ~6.2 nm”.

Study of near infra red femtosecond laser induced particles using transmission electron microscopy and low pressure impaction: Implications for laser ablation–inductively coupled plasma-mass spectrometry analysis of natural monazite

The characteristics of infra red femtosecond laser-induced aerosols are studied for monazite (LREE, Th(PO 4)) ablation and correlations are established with inductively coupled plasma-mass spectrometry (ICP-MS) signals. Critical parameters are tested within wide ranges of values in order to cover the usual laser ablation -ICP-MS analysis conditions: pulse energy (0.15 < E 0 < 1 mJ/pulse), pulse width (60 < τ < 3000 fs), ablation time ( t ≤ 10 min) and transport length ( l ≤ 6.3 m). Transmission electron microscopy reveals that aerosols are made of agglomerates of ~ 10 nm particles and 20–300 nm phosphorus depleted condensed spherical particles. These structures are not affected by any laser ablation parameter. Particle counting is performed using electronic low pressure impaction. Small changes on particle size distribution are noticed. They may be induced either by a peak of ablation rate in the first 15 s at high fluence (larger particles) or the loss of small particles during transport. We found a positive correlation between I (ICP-MS mean signal intensity in cps) and N (particle density in cm − 3 ) when varying E 0 and t, suggesting that N is controlled by the irradiance ( P 0 in W·cm − 2 ). Elemental ratio measurements show a steady state signal after the initial high ablation rate (mass load effect in the plasma torch) and before a late chemical fractionation, induced by poor extraction of bigger, early condensed spherical particles from the deepening crater. Such chemical fractionation effects remain within uncertainties, however. These effects can be limited by monitoring E 0 to shorten the initial transient state and delay the attainment of an unfavorable crater aspect ratio. Most adopted settings are for the first time deduced from aerosol characteristics, for infra red femtosecond laser ablation. A short transport ( l < 4.0 m) limits the agglomeration of particles by collision process along the tube. Short τ is preferred because of higher P 0 , yet no benefit is found on ICP-MS signal intensity under 200 fs. Under such pulse widths the increased particle production induces more agglomeration during transport, thereby resulting in higher mass load effects that reduce the ionization efficiency of the plasma torch. Thus, pulse energy must be set to get an optimal balance between the need for a high signal/background ratio and limitation of mass load effects in the plasma torch.

Skykomish River, Washington: Impact of ongoing glacier retreat on streamflow

AbstractGlacier retreat and changes in summer runoff have been pronounced in the Skykomish River Basin, North Cascades, Washington from 1950 to 2009. An analysis comparing USGS streamflow records for the 1950–1985 to the 1985–2009 period indicates that during the recent period the Skykomish River summer streamflow (July–September) has declined 26% in the watershed, spring runoff (April–June) has declined 6%, while winter runoff (November–March) has increased 10%. The minimum mean monthly August discharge from 1928 to 2010 occurred in 2003 and 2005 when streamflow was 15·1 and 15·2 m3s−1, respectively. From 1929 to 1985, streamflow was less than 14 m3s−1 during the glacier melt season on a single day in 1951. From 1986 to 2007 there were 217 days with discharge below 14 m3s−1 with 9 periods lasting for 10 consecutive days. In the Skykomish River watershed from 1958 to 2009, glacier area declined from 3·8 to 2·1 km2. Columbia, Foss, Hinman and Lynch Glacier, the primary glaciers in the basin, declined in area by 10, 60, 90 and 35%, respectively, since 1958. Annual mass balance measurements completed from 1984 to 2009 on Columbia, Foss and Lynch Glacier indicate a mass loss of 13·1 m w.e. Despite 15% higher ablation rates during the 1985–2009 period, the 45% reduction in glacier area led to a 38% reduction in glacier runoff between 1958 and 2009. The 38% reduction in glacier runoff did not lead to a significant decline in the percentage summer runoff contributed by glaciers under average conditions; the contribution has remained in the range of 1–3% from July to September. The glacier runoff decline impacted river discharge only during low flow periods in August and September. In August 2003 and 2005, glacier ablation contributed 1·5–1·6 m3s−1 to total discharge, or 10–11% of August discharge. While declining glacier area in the region has and will lead to reduced glacier runoff and reduced late summer streamflow, it has limited impact on the Skykomish River except during periods of critically low flow, below 14 m3s−1 when glaciers currently contribute more than 10% of the streamflow. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Clinical evaluation of ultrasound-guided percutaneous microwave ablation of hepatocellular carcinoma adjacent to the gastrointestinal tract

The purpose of the study was to prospectively evaluate safety and assisted with ethanol injection for hepatocellular carcinoma abutting gastrointestinal tract. 263 patients with 319 hepatic tumors that underwent percutaneous microwave ablation with curative intention were included. 101 lesions located less than 5 mm from gastrointestinal tract were in gastrointestinal group. 218 lesions located more than 5 mm from hepatic surface, gastrointestinal tract and first or second branch of hepatic vessels were in control group. The temperature of marginal ablation tissue proximal to gastrointestinal tract was monitored and controlled to fluctuating between 45 degrees C and 59 degrees C for more than 10 min for tumors in the gastrointestinal group. Ethanol (1-21 ml) was injected into marginal tissue in 62 of 101 lesions of the G1 group. 96 of 101 tumors (95.0%) in the gastrointestinal group and 208 of 218 tumors (95.4%) in the control group achieved complete ablation (P = 0.89). Local tumor progression for all the tumors were in the first year and the 6-,12- month local tumor progression rate in the gastrointestinal group and the control group were 6.9%, 11.9% and 7.3%, 8.3%, respectively (P = 0.21). There were neither immediate nor periprocedural complications in both groups. There was no delayed complication of gastrointestinal and bile ducts injury. Tumor seeding happened in one (1.1%) of the gastrointestinal group and three (1.8%) of the control group (P = 0.92). Under strict temperature monitoring, microwave ablation assisted with ethanol injection is safe and achieves a high complete ablation rate for hepatocellular carcinoma adjacent to gastrointestinal tract.

Metal Ablation with Short and Ultrashort Laser Pulses

In laser microstructuring there is a general conflict between precision and efficiency. Short pulsed micro- and nanosecond systems generally allow high ablation rates. Yet, thermal damage of the workpiece cannot be avoided completely. Ultrafast picoand femtosecond systems allow a higher precision, yet at lower ablation efficiency. This on the one hand can be attributed to the generally lower medium laser power of the ultrafast laser systems, on the other hand to the changed ablation mechanisms. In this contribution a comparative study of the ablation of metal with micro-, nano-, pico- and femtosecond laser pulses shall be presented

Parametric Study of Ablation Depths for Different Optical Glasses Using High Fluence Laser Induced Plasma Assisted Ablation (LIPAA)

A 40W Nd:YAG laser has been used to carry out parametric study the etching depth (ablation depth) for different optical glasses using stainless steel, brass and silver as target materials by Laser Induced Plasma Assisted Ablation (LIPAA) process. A maximum ablation depth of 38m for fused quartz has been achieved with stainless steel as target material with a high ablation rate of 565nm/pulse. A surface roughness of 120nm has been measured for fused quartz with stainless steel as target.

Study of surface energy and mass balance at the edge of the Antarctic ice sheet during summer in Dronning Maud Land, East Antarctica

This study estimates energy and mass balance at the edge of the Antarctic ice sheet close to a non-glaciated area. An automatic weather station was installed on the ice sheet, near an ice free area of Schirmacher Oasis in Dronning Maud Land, East Antarctica. Hourly snow-meteorological parameters were recorded and observed during the summer of the year 2007―08. Hourly radiative and turbulent energy fluxes were estimated at the ice surface. An ultrasonic sensor was used to measure accumulation or ablation at the glacier surface. Ground Penetrating Radar was also used to measure the changes in ice thickness at the observation point. The net radiative flux was the main heat source and the latent heat flux was the main heat sink for the ice sheet with seasonal average values of 98 W m -2 and -86.7 W m -2 respectively. There was a high ablation rate for the ice sheet near the non-glaciated area with a seasonal mean of 0.0172 m w.e. per day. Over the period 10 November 2007―7 February 2008 the mass balance was -1.53 m w.e. Good correlation (r 2 = 0.97) was observed between estimated and observed hourly ablation of the glacier. Sublimation and melt processes contributed 16.5% and 83.5% respectively to the net summer ablation.